How to test push notifications in simulator and production iOS apps

Issue #682

After has recently reminded about his updating APNs provider API which makes me realised a lot has changed about push notifications, both in terms of client and provider approach.

The HTTP/2-based Apple Push Notification service (APNs) provider API lets you take advantage of great features, such as authentication with a JSON Web Token, improved error messaging, and per-notification feedback. If you send push notifications with the legacy binary protocol, we strongly recommend upgrading to the APNs provider API.

From the the iOS client point of view, you pretty much don’t need to care about provider API, as you only need to register for push notification capability and send the device token to your backend, and it’s the backend’s job to send push request to Apple notifications server.

But it’s good to know the underlying mechanism, especially when you want to troubleshoot push notification. Since a push notification failure can be because of many reasons: it could be due to some failed logic in your backend, or that the push certificate has expired, or that you have sent the wrong device token, or that user has turned off push permission in Settings app, or that the push has been delayed.

Here’s also a common abbreviations you need to learn: APNs it is short for Apple Push Notification service. You can think of it as the server your device always has connection with, so you’re ready for any server push messages from it.

What is binary provider API

Push notification feature was first introduced by Apple in 2009 via a fairly complex binary provider API

binary

In short, binary provider API is just a specification about which address and which format to send push request to Apple push server. The binary interface of the production environment is available through gateway.push.apple.com, port 2195 and development environment gateway.sandbox.push.apple.com, port 2195. The binary interface employs a plain TCP socket for binary content that is streaming in nature.

As you can see in the package instruction above, we need specify frame length and data. Data is a key value pairs of multiple informations like device token, expiration, topic, priority.

Send request to the above addresses via secured TLS or SSL channel. The SSL certificate required for these connections is obtained from your developer account.

The new HTTP/2 provider API

The new HTTP2/ provider API is recommended, it has detailed error reporting and better throughput. If you use URLSession which supports the HTTP/1.1 and HTTP/2 protocols. HTTP/2 support, as described by RFC 7540, you will feel familiar.

In short, when you have a notification to send to a user, your provider must construct a POST request and send it to Apple Push Notification service (APNs). Your request must include the following information:

  • The JSON payload that you want to send
  • The device token for the user’s device
  • Request-header fields specifying how to deliver the notification
  • For token-based authentication, your provider server’s current authentication token

Upon receiving your server’s POST request, APNs validates the request using either the provided authentication token or your server’s certificate. If validation succeeds, APNs uses the provided device token to identify the user’s device. It then tries to send your JSON payload to that device.

So it’s pretty much how you configure URLRequestwith URLSession, specify base url, some request headers including the authorization and the payload body.

Use HTTP/2 and TLS 1.2 or later to establish a connection to the new provider API endpoint. For development serverit is api.sandbox.push.apple.com:443 and for production server it is api.push.apple.com:443. You then send the request as POST and Apple will do its job to verify and send the push notification to the users device.

Certificate vs token based authentication

To send push request to APNs, you need to authenticate to tell that is really from you. APNs support 2 types of authentication, the traditional way with a certificate, and the recently new recommended way with a p8 token.

Certificate based authentication

For certificate based authentication, you will need a p12 certificate which you can obtain and generate from your Developer account.

cer

Because there are sandbox and production push endpoint, few years ago it was required to have separate sandbox and production environment push certificate, which you had to create separately in your Apple developer account, then in testing need to specify the correct push certificate for each environment.

Now around iOS 10 year we can use just 1 single certificate for both sandbox and production, which is a relief for us developers. When we create certificate on Apple developer page, we need to upload a certificate signing request that we can generate from Keychain Access app. After we download the generated push certificate, download and run it in Keychain, there we can generate p12 key file that contains both certificate and private key to sign our push request.

Certificate and provisioning profiles valid for only 1 year. So every year you have to renew push notification certificates, which is also a good and bad thing. Besides that, every app differs from bundle id, so we kinda have to generate certificate for each app.

Token based authentication

Token-based authentication offers a stateless way to communicate with APNs. Stateless communication is faster than certificate-based communication because it doesn’t require APNs to look up the certificate, or other information, related to your provider server. There are other advantages to using token-based authentication:

The cool thing about token is that you can use one token to distribute notifications for all of your company’s apps. You can create in your Apple developer account. Key authentication is the recommended way to authenticate with Apple services, so it is used not only for push services, but also for MusicKit and DeviceCheck.

key

When you request a key, Apple gives you a 10-character string with the Key ID which you must include this string in your JSON tokens and an authentication token signing key, specified as a text file (with a .p8 file extension). The key is allowed to download once and you need to keep it properly.

The token that you include with your notification requests uses the JSON Web Token (JWT) specification. The token itself contains four key-value pairs

Screenshot 2020-10-11 at 06 28 34

After all, the JSON Web Token is encoded in this authorization HTTP headers in your request like this

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authorization = bearer eyAia2lkIjogIjhZTDNHM1JSWDciIH0.eyAiaXNzIjogIkM4Nk5WOUpYM0QiLCAiaWF0I
jogIjE0NTkxNDM1ODA2NTAiIH0.MEYCIQDzqyahmH1rz1s-LFNkylXEa2lZ_aOCX4daxxTZkVEGzwIhALvkClnx5m5eAT6
Lxw7LZtEQcH6JENhJTMArwLf3sXwi

For security, APNs requires you to refresh your token regularly. Refresh your token no more than once every 20 minutes and no less than once every 60 minutes.

How to register for push notifications from iOS app

The APIs to register for remote notification has changed over the years.

iOS 7

In iOS 7, we used to use this method registerForRemoteNotificationTypes to register to receive remote notifications of the specified types via Apple Push Notification service.

The types can be UIRemoteNotificationTypeBadge, UIRemoteNotificationTypeAlert, UIRemoteNotificationTypeSound

When you send this message, the device initiates the registration process with Apple Push Notification service. If it succeeds, the app delegate receives a device token in the application:didRegisterForRemoteNotificationsWithDeviceToken: method; if registration doesn’t succeed, the delegate is informed via the application:didFailToRegisterForRemoteNotificationsWithError:method. If the app delegate receives a device token, it should connect with its provider and pass it the token.

iOS 8 with registerUserNotificationSettings

From iOS 8, there’s separation between asking for a remote notification with device token, and with presenting push message to the user. This confused developers as these 2 things are separate now.

First, we use registerForRemoteNotifications to register to receive remote notifications via Apple Push Notification service.

Call this method to initiate the registration process with Apple Push Notification service. If registration succeeds, the app calls your app delegate object’s application(_:didRegisterForRemoteNotificationsWithDeviceToken:) method and passes it a device token. You should pass this token along to the server you use to generate remote notifications for the device. If registration fails, the app calls its app delegate’s application(_:didFailToRegisterForRemoteNotificationsWithError:) method instead.

In short, this is to receive device token from APNs so we can do silent push notification or other things. Note that we need to enable Remote notification capability for Background modes.

Screenshot 2020-10-11 at 06 39 46

To present push message to user via alert, banner, badge or sound, we need to explicitly ask for using this method registerUserNotificationSettings to registers your preferred options for notifying the user.

If your app displays alerts, play sounds, or badges its icon, you must call this method during your launch cycle to request permission to alert the user in these ways. After calling this method, the app calls the application(_ application: UIApplication, didRegister notificationSettings: UIUserNotificationSettings) method of its app delegate to report the results. You can use that method to determine if your request was granted or denied by the user.

iOS 10 with UserNotifications framework

In iOS 10, Apple introduced UserNotifications and UserNotificationsUI framework and lots of new features to push notifications like actions and attachments.

To ask for permission to present push message from iOS 10, use the new UNUserNotificationCenter which accepts options and block callback with grant status.

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UNUserNotificationCenter.current().requestAuthorization(options: [.badge, .sound, .alert])

abc

There ‘s also UNNotificationAction and UNNotificationAttachment to specify additional actions and attachment to go along with the push message, this is very handy for visual purpose and convenient actions user can perform right away from the push message.

There’s also a convenient UserNotificationsUI that was shipped with iOS 10 that allows us to embed custom view controller from our push message

ui

When an iOS device receives a notification containing an alert, the system displays the contents of the alert in two stages. Initially, it displays an abbreviated banner with the title, subtitle, and two to four lines of body text from the notification. If the user presses the abbreviated banner, iOS displays the full notification interface, including any notification-related actions. The system provides the interface for the abbreviated banner, but you can customize the full interface using a notification content app extension.

Also, there is this callback userNotificationCenter _:willPresent that asks the delegate how to handle a notification that arrived while the app was running in the foreground.

If your app is in the foreground when a notification arrives, the shared user notification center calls this method to deliver the notification directly to your app. If you implement this method, you can take whatever actions are necessary to process the notification or show it when your app is running.

iOS 12 with provisional push

New in iOS 12 is the UNAuthorizationStatus.provisional, which are notifications that appear silently in the user’s notification center without appearing on the user’s home screen. We can start sending them as soon as a user has downloaded and run your app for the first time. You can send provisional push notifications unlimited times unless the user explicitly turns them off.

Screenshot 2020-10-11 at 06 58 34

This is good to send unobtrusive push to users in their Notification Center where they can pick up at a later time.

iOS 13 with apns-push-type

Starting with iOS 13 and watchOS 6, there is apns-push-type which must accurately reflect the contents of your notification’s payload. If there is a mismatch, or if the header is missing on required systems, APNs may return an error.

The apns-push-type header field has six valid values. The descriptions below describe when and how to use these values. For example alert for notifications that trigger a user interaction and background for notifications that deliver content in the background.

In a WWDC 2019 session Advances in App Background Execution, apns-priority must be set to 5 for content available notifications.

iOS 14 with ephemeral authorization status and AppClip

From Enable your App Clip to schedule and receive notifications for a short or extended time period.

Some App Clips may need to schedule or receive notifications to provide value. Consider an App Clip that allows users to order food for delivery: By sending notifications, the App Clip informs the user about an upcoming delivery. If notifications are important for your App Clip’s functionality, enable it to schedule or receive notifications for up to 8 hours after each launch.

Remote notification only with content-available

Besides user interface notification, there is content-available notification that delivers notifications that wake your app and update it in the background. If your app’s server-based content changes infrequently or at irregular intervals, you can use background notifications to notify your app when new content becomes available. Read Pushing Background Updates to Your App

Testing push notification in simulator

We have been able to drag images to the Photos app in simulator for years, but new in Xcode 11.4 is the ability to drag push payload to simulator to simulate remote push notification.

All we have to do is create an apns file with Simulator Target Bundle key to specify our app, then drag to the simulator

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{
"Simulator Target Bundle": "com.onmyway133.PushHero",
"aps": {
"alert": "Welcome to Push Hero",
"sound": "chime",
"badge": 2
}
}

Many of the simulator features can be controlled via xcrun simctl command line tool where you can change status bar time, battery info, start and stop certain simulators and send push with xcrun simctl push. This is very handy in case you want to automate things.

Test push notification easily with Push Hero

As iOS developers who need to test push notification a lot, I face this challenge. That’s why I made Push Hero as a native macOS application that allows us to reliably test push notification. It is written in pure Swift with all the new APNs specification in mind.

Screenshot 2020-10-08 at 06 17 12

With Push Hero, we can setup multiple test scenario for different app. Each we can specify the authentication method we want, either with p8 token or p12 certificate based. There’s also input validation and hint helper that explains which field is needed and in which format, so you save time to work on your push testing instead.

New in latest version of Push Hero is the ability to send multiple pushes to multiple device tokens, which is the most frequent request. In the right history pane, there’s information about each request and response content, together with apns id information.

Also in Push Hero is the popup to show explanation for each field, and you need to consult Sending Notification Requests to APNs documentation as there are some specifications there. For example with VoIP push, the apns-topic header field must use your app’s bundle ID with .voip appended to the end. If you’re using certificate-based authentication, you must also register the certificate for VoIP services

Conclusion

Push notification continues to be important for iOS apps, and Apple has over the years improved and changed it for the better. This also means lots of knowledge to keep up with. Understanding provider APNs, setting up certificate and JSON Web Token key can be intimidating and take time.

Hopefully the above summary gets you more understanding into push notification, not only the history of changes in both client and provider API, but also some ways to test it easily.

How to draw arc corner using Bezier Path

Issue #673

To draw rounded 2 corners at top left and top right, let’s start from bottom left

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let path = UIBezierPath()
// bottom left
path.move(to: CGPoint(x: 0, y: bounds.height))
// top left corner
path.addArc(withCenter: CGPoint(x: radius, y: radius), radius: radius, startAngle: CGFloat.pi, endAngle: CGFloat.pi * 3 / 2, clockwise: true)
// top right corner
path.addArc(withCenter: CGPoint(x: bounds.width - radius, y: radius), radius: radius, startAngle: CGFloat.pi * 3 / 2, endAngle: 0, clockwise: true)
// bottom right
path.addLine(to: CGPoint(x: bounds.width, y: bounds.height))
path.close()
Screenshot 2020-09-15 at 14 16 01

cc

Read more

How to make dynamic font size for UIButton

Issue #671

Use adjustsFontForContentSizeCategory

A Boolean that indicates whether the object automatically updates its font when the device’s content size category changes.

If you set this property to YES, the element adjusts for a new content size category on a UIContentSizeCategoryDidChangeNotification.

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button.titleLabel?.adjustsFontForContentSizeCategory = true
button.backgroundColor = UIColor.green
button.titleLabel?.font = UIFont.preferredFont(forTextStyle: .title1)

label.adjustsFontForContentSizeCategory = true
label.backgroundColor = UIColor.yellow
label.font = UIFont.preferredFont(forTextStyle: .title1)

However it seems view (UIButton or UILabel) size is the same, just the inner text increases in size. A workaround is to put view inside UIStackView so UIButton or UILabel can automatically changes size.

How to test for view disappear in navigation controller

Issue #670

To test for viewWillDisappear during UINavigationController popViewController in unit test, we need to simulate UIWindow so view appearance works.

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final class PopTests: XCTestCase {
func testPop() {
let window = UIWindow(frame: UIScreen.main.bounds)
let navigationController = UINavigationController()
window.rootViewController = navigationController
let viewController = DetailViewController()

navigationController.viewControllers = [
UIViewController(),
viewController
]

window.makeKeyAndVisible()
let expectation = XCTestExpectation()
navigationController.popViewController(animated: false)
DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
XCTAssertTrue(viewController.wasDismissed)
expectation.fulfill()
}
wait(for: [expectation], timeout: 1)
}
}
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class DetailViewController: UIViewController {
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if isMovingFromParent {
wasDismissed = true
}
}
}

How to set text color for UIDatePicker

Issue #660

Apply tintColor does not seem to have effect.

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datePicker.setValue(UIColor.label, forKeyPath: "textColor")
datePicker.setValue(false, forKey: "highlightsToday")

How to use background in iOS

Issue #631

beginBackgroundTask

https://developer.apple.com/documentation/uikit/app_and_environment/scenes/preparing_your_ui_to_run_in_the_background/extending_your_app_s_background_execution_time

When your app moves to the background, the system calls your app delegate’s applicationDidEnterBackground(_:) method. That method has five seconds to perform any tasks and return. Shortly after that method returns, the system puts your app into the suspended state. For most apps, five seconds is enough to perform any crucial tasks, but if you need more time, you can ask UIKit to extend your app’s runtime.

You extend your app’s runtime by calling the beginBackgroundTask(withName:expirationHandler:) method. Calling this method gives you extra time to perform important tasks.

BackgroundTasks

Use the BackgroundTasks framework to keep your app content up to date and run tasks requiring minutes to complete while your app is in the background. Longer tasks can optionally require a powered device and network connectivity.

Register launch handlers for tasks when the app launches and schedule them as required. The system will launch your app in the background and execute the tasks.

The main API for using this framework is the BGTaskScheduler . This API constantly monitors the system state such as battery level, background usage, and more, so it chooses the optimal time to run your tasks.

To use this API, you begin working when your app is on the foreground. You need to create Background task request. The framework provides an abstract class BGTask, you never use this task directly. Instead, the framework provides two concrete subclasses you can interact with: BGProcessingTask, for long running and maintenance tasks such backup and cleanup, and BGAppRefreshTask to keep your app up-to-date throughout the day.

URLSession background

When you create your background download or upload tasks with URLSession, you’re actually scheduling a download (or upload) with the ‘nsurlsessiond’ which is a daemon service that runs as a separate process.

How to mask with UILabel

Issue #603

Need to set correct frame for mask layer or UILabel, as it is relative to the coordinate of the view to be masked

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let aView = UIView(frame: .init(x: 100, y: 110, width: 200, height: 100))

let textLayer = CATextLayer()
textLayer.foregroundColor = UIColor.white.cgColor
textLayer.string = "Hello world"
textLayer.font = UIFont.preferredFont(forTextStyle: .largeTitle)
textLayer.frame = aView.bounds

aView.layer.mask = textLayer

Use sizeToFit to ensure frame for UILabel

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let label = UILabel()
label.frame.origin = CGPoint(x: 80, y: 80)

label.textColor = UIColor.black
label.font = UIFont.preferredFont(forTextStyle: .largeTitle)
label.text = "ABC"
label.sizeToFit()

aView.mask = label

Change bounds.origin

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label.frame.origin = CGPoint(x: 50, y: 50)
aView.bounds.origin = label.frame.origin

Adding label to view hierarchy seems to remove masking effect. Need to set mask later

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view.addSubview(aView)
view.addSubview(label)
aView.mask = label

Can’t add overlayView to UILabel and use UILabel as mask, cause cycler CALayer

After using UILabel as mask, its superview is nil

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aView.mask = label
label.superview == nil

Mask with snapshot from UILabel. Need to set correct frame for aView and maskLayer

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let maskLayer = CALayer()
maskLayer.contents = label.makeScreenshot().cgImage
maskLayer.contentsGravity = .resizeAspect

aView.frame = label.bounds
maskLayer.frame = aView.bounds
aView.layer.mask = maskLayer
label.addSubview(aView)

extension UIView {
func makeScreenshot() -> UIImage {
let renderer = UIGraphicsImageRenderer(bounds: self.bounds)
return renderer.image { (context) in
self.layer.render(in: context.cgContext)
}
}
}

How to sync multiple CAAnimation

Issue #600

Use same CACurrentMediaTime

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final class AnimationSyncer {
static let now = CACurrentMediaTime()

func makeAnimation() -> CABasicAnimation {
let animation = CABasicAnimation(keyPath: "opacity")
animation.fillMode = .forwards
animation.fromValue = 0
animation.toValue = 1
animation.repeatCount = .infinity
animation.duration = 2
animation.beginTime = Self.now
animation.autoreverses = true
animation.timingFunction = CAMediaTimingFunction(name: .easeInEaseOut)
return animation
}
}

How to build SwiftUI style UICollectionView data source in Swift

Issue #598

It’s hard to see any iOS app which don’t use UITableView or UICollectionView, as they are the basic and important foundation to represent data. UICollectionView is very basic to use, yet a bit tedious for common use cases, but if we abstract over it, then it becomes super hard to customize. Every app is unique, and any attempt to wrap around UICollectionView will fail horribly. A sensable approach for a good abstraction is to make it super easy for normal cases, and easy to customize for advanced scenarios.

I’m always interested in how to make UICollectionView easier and fun to write and have curated many open sources here data source. Many of these data source libraries try to come up with totally different namings and complex paradigm which makes it hard to onboard, and many are hard to customize.

In its simplest form, what we want in a UICollectionView data source is cell = f(state), which means our cell representation is just a function of the state. We just want to set model to the cell, the correct cell, in a type safe manner.

Generic data source

The basic is to make a generic data source that sticks with a particular cell

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class DataSource<T>: NSObject {
let items: [T]
let configure: (T, UICollectionViewCell) -> Void
let select: (UICollectionViewCell, IndexPath) -> Void
}

This works for basic usage, and we can create multiple DataSource for each kind of model. The problem is it’s hard to subclass DataSource as generic in Swift and inheritance for ObjcC NSObject don’t work well.

Check for the types

Seeing the problem with generic data source, I’ve tried another approach with Upstream where it’s easier to declare sections and models.

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let sections: [Section] = [
Section(
header: Header(model: Model.header("Information"), viewType: HeaderView.self),
items: [
Item(model: Model.avatar(avatarUrl), cellType: AvatarCell.self),
Item(model: Model.name("Thor"), cellType: NameCell.self),
Item(model: Model.location("Asgard"), cellType: NameCell.self)
]
),
Section(
header: Header(model: Model.header("Skills"), viewType: HeaderView.self),
items: [
Item(model: Model.skill("iOS"), cellType: SkillCell.self),
Item(model: Model.skill("Android"), cellType: SkillCell.self)
]
)
]

adapter.reload(sections: sections)

This uses the Adapter pattern and we need to handle AdapterDelegate. To avoid the generic problem, this Adapter store items as Any, so we need to type cast all the time.

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extension ProfileViewController: AdapterDelegate {
func configure(model: Any, view: UIView, indexPath: IndexPath) {
guard let model = model as? Model else {
return
}

switch (model, view) {
case (.avatar(let string), let cell as Avatarcell):
cell.configure(string: string)
case (.name(let name), let cell as NameCell):
cell.configure(string: name)
case (.header(let string), let view as HeaderView):
view.configure(string: string)
default:
break
}
}
}

The benefit is that we can easily subclass this Adapter manager to customize the behaviour, here is how to make accordion

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class AccordionManager<T>: Manager<T> {
private var collapsedSections = Set<Int>()

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return collapsedSections.contains(section)
? 0 : sections[section].items.count
}

func toggle(section: Int) {
if collapsedSections.contains(section) {
collapsedSections.remove(section)
} else {
collapsedSections.insert(section)
}

let indexSet = IndexSet(integer: section)
tableView?.reloadSections(indexSet, with: .automatic)
}
}

SwiftUI

SwiftUI comes in iOS 13 with a very concise and easy to use syntax. SwiftUI has good diffing so we just need to update our models so the whole content will be diffed and rendered again.

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var body: some View {
List {
ForEach(blogs) { blog in
VStack {
Text(blog.name)
}
.onTap {
print("cell was tapped")
}
}
}
}

SwiftUI style with diffing

I built DeepDiff before and it was used by many people. Now I’m pleased to introduce Micro which is a SwiftU style with DeepDiff powered so it performs fast diffing whenever state changes.

With Micro we can just use the familiar forEach to declare Cell, and the returned State will tell DataSource to update the UICollectionView.

Every time state is assigned, UICollectionView will be fast diffed and reloaded. The only requirement is that your model should conform to DiffAware with diffId so DeepDiff knows how to diff for changes.

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let dataSource = DataSource(collectionView: collectionView)
dataSource.state = State {
ForEach(blogs) { blog in
Cell<BlogCell>() { context, cell in
cell.nameLabel.text = blog.name
}
.onSelect { context in
print("cell at index \(context.indexPath.item) is selected")
}
.onSize { context in
CGSize(
width: context.collectionView.frame.size.width,
height: 40
)
}
}
}

DataSource is completely overridable, if you want to customize any methods, just subclass DataSource, override methods and access its state.models

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class CustomDataSource: DataSource {
override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let blog = state.models[indexPath.item] as? Blog
print(blog)
}
}

Diffable data source in iOS 13

In iOS 13, Apple adds Using Collection View Compositional Layouts and Diffable Data Sources which is very handy.

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func makeDataSource() -> UITableViewDiffableDataSource<Section, Contact> {
let reuseIdentifier = cellReuseIdentifier

return UICollectionViewDiffableDataSource(
collectionView: collectionView,
cellProvider: { collectionView, indexPath, blog in
let cell = tableView.dequeueReusableCell(
withIdentifier: reuseIdentifier,
for: indexPath
)

cell.textLabel?.text = blog.name
cell.detailTextLabel?.text = blog.email
return cell
}
)
}

This is iOS 13+ only, and the main components are the cellProvider acting as cellForItemAtIndexPath, and the snapshot for diffing. It also supports section.

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let snapshot = NSDiffableDataSourceSnapshot<Section, Blog>()
dataSource.apply(snapshot, animatingDifferences: animate)

How to test drag and drop in UITests

Issue #583

In UITests, we can use press from XCUIElement to test drag and drop

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let fromCat = app.buttons["cat1"].firstMatch
let toCat = app.buttons["cat2"]
let fromCoordinate = fromCat.coordinate(withNormalizedOffset: CGVector(dx: 0, dy: 0))
let toCoordinate = toCat.coordinate(withNormalizedOffset: CGVector(dx: 0, dy: -0.5))
fromCoordinate.press(forDuration: 1, thenDragTo: toCoordinate)

and then take screenshot

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let screenshot = XCUIScreen.main.screenshot()
let attachment = XCTAttachment(screenshot: screenshot)
attachment.lifetime = .keepAlways
attachment.name = name
add(attachment)

Screenshot capturing happens after the action, so it may be too late. One way is to inject launch arguments, like app.launchArguments.append("--dragdrop") to alter some code in the app.

We can also swizzle gesture recognizer to alter behavior

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extension UILongPressGestureRecognizer {
@objc var uiTests_state: UIGestureRecognizer.State {
let state = self.uiTests_state
if state == .ended {
return .changed
} else {
return state
}
}
}

let originalSelector = #selector(getter: UILongPressGestureRecognizer.state)
let swizzledSelector = #selector(getter: UILongPressGestureRecognizer.uiTests_state)

let originalMethod = class_getInstanceMethod(UILongPressGestureRecognizer.self, originalSelector)!
let swizzledMethod = class_getInstanceMethod(UILongPressGestureRecognizer.self, swizzledSelector)!

let didAddMethod = class_addMethod(UILongPressGestureRecognizer.self, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))

if didAddMethod {
class_replaceMethod(UILongPressGestureRecognizer.self, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod))
} else {
method_exchangeImplementations(originalMethod, swizzledMethod)
}

How to set corner radius in iOS

Issue #582

Use View Debugging

Run on device, Xcode -> Debug -> View debugging -> Rendering -> Color blended layer
On Simulator -> Debug -> Color Blended Layer

Corner radius

Okay. Talked to a Core Animation engineer again:

  • cornerRadius was deliberately improved in Metal so it could be used everywhere.
  • Using a bitmap is WAY heavier in terms of memory and performance.
  • CALayer maskLayer is still heavy.

https://developer.apple.com/documentation/quartzcore/calayer/1410818-cornerradius

Setting the radius to a value greater than 0.0 causes the layer to begin drawing rounded corners on its background. By default, the corner radius does not apply to the image in the layer’s contents property; it applies only to the background color and border of the layer. However, setting the masksToBounds property to true causes the content to be clipped to the rounded corners.

https://developer.apple.com/documentation/quartzcore/calayer/1410896-maskstobounds

When the value of this property is true, Core Animation creates an implicit clipping mask that matches the bounds of the layer and includes any corner radius effects. If a value for the mask property is also specified, the two masks are multiplied to get the final mask value.

Mask layer

layer.cornerRadius, with or without layer.maskedCorners causes blending
Use mask layer instead of layer.cornerRadius to avoid blending, but mask causes offscreen rendering

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let mask = CAShapeLayer()
let path = UIBezierPath(
roundedRect: bounds,
byRoundingCorners: [.topLeft, .topRight, .bottomLeft, .bottomRight],
cornerRadii: CGSize(width: 20, height: 20)
)
mask.path = path.cgPath
layer.mask = mask

Offscreen rendering

Instruments’ Core Animation Tool has an option called Color Offscreen-Rendered Yellow that will color regions yellow that have been rendered with an offscreen buffer (this option is also available in the Simulator’s Debug menu). Be sure to also check Color Hits Green and Misses Red. Green is for whenever an offscreen buffer is reused, while red is for when it had to be re-created.

Offscreen drawing on the other hand refers to the process of generating bitmap graphics in the background using the CPU before handing them off to the GPU for onscreen rendering. In iOS, offscreen drawing occurs automatically in any of the following cases:

Core Graphics (any class prefixed with CG)
The drawRect() method, even with an empty implementation.
CALayers with a shouldRasterize property set to YES.
CALayers using masks (setMasksToBounds) and dynamic shadows (setShadow
).
Any text displayed on screen, including Core Text.
Group opacity (UIViewGroupOpacity).

Instruments

Read more

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@abstract Sets the corner rounding method to use on the ASDisplayNode.
There are three types of corner rounding provided by Texture: CALayer, Precomposited, and Clipping.

- ASCornerRoundingTypeDefaultSlowCALayer: uses CALayer's inefficient .cornerRadius property. Use
this type of corner in situations in which there is both movement through and movement underneath
the corner (very rare). This uses only .cornerRadius.

- ASCornerRoundingTypePrecomposited: corners are drawn using bezier paths to clip the content in a
CGContext / UIGraphicsContext. This requires .backgroundColor and .cornerRadius to be set. Use opaque
background colors when possible for optimal efficiency, but transparent colors are supported and much
more efficient than CALayer. The only limitation of this approach is that it cannot clip children, and
thus works best for ASImageNodes or containers showing a background around their children.

- ASCornerRoundingTypeClipping: overlays 4 separate opaque corners on top of the content that needs
corner rounding. Requires .backgroundColor and .cornerRadius to be set. Use clip corners in situations
in which is movement through the corner, with an opaque background (no movement underneath the corner).
Clipped corners are ideal for animating / resizing views, and still outperform CALayer.

Generally, on iOS, pixel effects and Quartz / Core Graphics drawing are not hardware accelerated, and most other things are.
The following things are not hardware accelerated, which means that they need to be done in software (offscreen):
Anything done in a drawRect. If your view has a drawRect, even an empty one, the drawing is not done in hardware, and there is a performance penalty.
Any layer with the shouldRasterize property set to YES.
Any layer with a mask or drop shadow.
Text (any kind, including UILabels, CATextLayers, Core Text, etc).
Any drawing you do yourself (either onscreen or offscreen) using a CGContext.

For example, writing your own draw method with Core Graphics means your rendering will technically be done in software (offscreen) as opposed to being hardware accelerated like it is when you use a normal CALayer. This is why manually rendering a UIImage with a CGContext is slower than just assigning the image to a UIImageView.

if layer’s contents is nil or this contents has a transparent background, you just need to set cornerRadius. For UILabel, UITextView and UIButton, you can just set layer’s backgroundColor and cornerRadius to get a rounded corner. Note: UILabel’s backgroundColor is not its layer’s backgroundColor.

How to work with SceneDelegate in iOS 12

Issue #580

Events

open url

Implement scene(_:openURLContexts:) in your scene delegate.

If the URL launches your app, you will get scene(_:willConnectTo:options:) instead and it’s in the options.

life cycle

Here’s how it works: If you have an “Application Scene Manifest” in your Info.plist and your app delegate has a configurationForConnectingSceneSession method, the UIApplication won’t send background and foreground lifecycle messages to your app delegate. That means the code in these methods won’t run:

applicationDidBecomeActive
applicationWillResignActive
applicationDidEnterBackground
applicationWillEnterForeground
The app delegate will still receive the willFinishLaunchingWithOptions: and didFinishLaunchingWithOptions: method calls so any code in those methods will work as before.

UIApplication notifications

Notifications still trigger in iOS 13 if adopting SceneDelegate

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UIApplication.didBecomeActiveNotification
UIApplication.willResignActiveNotification

https://developer.apple.com/documentation/uikit/app_and_environment/scenes/preparing_your_ui_to_run_in_the_foreground

Use foreground transitions to prepare your app’s UI to appear onscreen. An app’s transition to the foreground is usually in response to a user action. For example, when the user taps the app’s icon, the system launches the app and brings it to the foreground. Use a foreground transition to update your app’s UI, acquire resources, and start the services you need to handle user requests.

All state transitions result in UIKit sending notifications to the appropriate delegate object:

In iOS 13 and later—A UISceneDelegate object.
In iOS 12 and earlier—The UIApplicationDelegate object.

You can support both types of delegate objects, but UIKit always uses scene delegate objects when they are available. UIKit notifies only the scene delegate associated with the specific scene that is entering the foreground. For information about how to configure scene support, see Specifying the Scenes Your App Supports.

keyWindow

Show most recent activeUIWindow

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UIApplication.shared.keyWindow

This property holds the UIWindow object in the windows array that is most recently sent the makeKeyAndVisible() message.

AppDelegate vs SceneDelegate

Get sceneDelegate from AppDelegate

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UIApplication.shared.openSessions.first?.scene?.delegate

order

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SceneDelegate.sceneDidBecomeActive
UIApplication.didBecomeActiveNotification
SceneDelegate.sceneWillResignActive
UIApplication.willResignActiveNotification

Read more

How to get updated safeAreaInsets in iOS

Issue #570

Use viewSafeArea

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@available(iOS 11.0, *)
override func viewSafeAreaInsetsDidChange() {
super.viewSafeAreaInsetsDidChange()

self.collectionView.reloadData()
}

Use https://developer.apple.com/documentation/uikit/uiview/2891102-safearealayoutguide

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view.safeAreaLayoutGuide.layoutFrame

https://developer.apple.com/documentation/uikit/uiview/2891103-safeareainsets

For the view controller’s root view, the insets account for the status bar, other visible bars, and any additional insets that you specified using the additionalSafeAreaInsets property of your view controller. For other views in the view hierarchy, the insets reflect only the portion of the view that is covered. For example, if a view is entirely within the safe area of its superview, the edge insets in this property are 0.

Use UICollectionView.contentInsetAdjustmentBehavior

Nested view

For UICollectionView inside Cell inside UICollectionView, its insets is 0, but its parent parent is correct, which is the original cell

UICollectionView -> Cell -> ContentView -> UICollectionView

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collectionView.superview?.superview?.safeAreaInsets

viewWillAppear: safeAreaInsets is not set to collectionView
viewDidAppear: safeAreaInsets is set to collectionView and cells, but not to nested collectionView

In viewSafeAreaInsetsDidChange, invalidate outer and nested collectionViewLayout

Use extendedLayoutIncludesOpaqueBars

https://developer.apple.com/documentation/uikit/uiviewcontroller/1621404-extendedlayoutincludesopaquebars

A Boolean value indicating whether or not the extended layout includes opaque bars.

Seems to affect left and right insets

But it’s not, it is because of when safeAreaInsets is available, and how it is passed to nested view

When invalidating collection view layout with custom UIPresentationController, alongsideTransition is called twice, the first time with old safeAreaInsets, and the second time with latest safeAreaInsets

And the layout invalidation uses the old insets.

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override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
super.viewWillTransition(to: size, with: coordinator)
coordinator.animate(alongsideTransition: { _ in
self.collectionViewLayout.invalidateLayout()
})
}

Dispatch

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// UIViewController subclass
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
super.viewWillTransition(to: size, with: coordinator)
coordinator.animate(alongsideTransition: { _ in
DispatchQueue.main.async {
self.collectionViewLayout.invalidateLayout()
}
})
}

Call layoutIfNeeded

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// UIPresentationController subclass
override var frameOfPresentedViewInContainerView: CGRect {
guard let containerView = containerView else { return .zero }

presentedView?.setNeedsLayout()
presentedView?.layoutIfNeeded()

return ...

Check

Check that UICollectionView or the view you’re working on is in view hierarchy

Check that you’re using code in viewDidLayoutSubviews when safeAreaInsets is known

Read more

How to disable implicit decoration view animation in UICollectionView

Issue #569

From documentation https://developer.apple.com/documentation/uikit/uicollectionviewlayout/1617726-initiallayoutattributesforappear

This method is called after the prepare(forCollectionViewUpdates:) method and before the finalizeCollectionViewUpdates() method for any decoration views that are about to be inserted. Your implementation should return the layout information that describes the initial position and state of the view. The collection view uses this information as the starting point for any animations. (The end point of the animation is the view’s new location in the collection view.) If you return nil, the layout object uses the item’s final attributes for both the start and end points of the animation.

The default implementation of this method returns nil.

Although the doc says “The default implementation of this method returns nil”, calling super.initialLayoutAttributesForAppearingDecorationElement gives somehow implicit animation. The workaround is to explicitly return nil

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func initialLayoutAttributesForAppearingDecorationElement(ofKind elementKind: String, at decorationIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
return nil
}

func finalLayoutAttributesForDisappearingDecorationElement(ofKind elementKind: String, at decorationIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
return nil
}

Decoration seems to be removed when all items are removed. Workaround is to check and only add decoration when there is preferred data or cell

How to make simple adapter for delegate and datasource for UICollectionView and UITableView

Issue #567

Code

Make open Adapter

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import UIKit

public protocol AdapterDelegate: class {

/// Apply model to view
func configure(model: Any, view: UIView, indexPath: IndexPath)

/// Handle view selection
func select(model: Any)

/// Size the view
func size(model: Any, containerSize: CGSize) -> CGSize
}

/// Act as DataSource and Delegate for UICollectionView, UITableView
open class Adapter: NSObject,
UICollectionViewDataSource, UICollectionViewDelegateFlowLayout,
UITableViewDataSource, UITableViewDelegate {

public var sections: [Section] = []
public weak var collectionView: UICollectionView?
public weak var tableView: UITableView?
public weak var delegate: AdapterDelegate?

let registryService = RegistryService()

// MARK: - Initialiser
public required init(collectionView: UICollectionView) {
self.collectionView = collectionView
super.init()
}

public required init(tableView: UITableView) {
self.tableView = tableView
super.init()
}

// MARK: - UICollectionViewDataSource
open func numberOfSections(in collectionView: UICollectionView) -> Int {
return sections.count
}

open func collectionView(_ collectionView: UICollectionView,
numberOfItemsInSection section: Int) -> Int {
return sections[section].items.count
}

open func collectionView(_ collectionView: UICollectionView,
cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let item = sections[indexPath.section].items[indexPath.row]
let cell = collectionView.dequeueReusableCell(
withReuseIdentifier: item.cellType.typeName,
for: indexPath)

delegate?.configure(model: item.model, view: cell, indexPath: indexPath)

return cell
}

open func collectionView(
_ collectionView: UICollectionView,
viewForSupplementaryElementOfKind kind: String,
at indexPath: IndexPath) -> UICollectionReusableView {

if let header = sections[indexPath.section].header,
kind == UICollectionElementKindSectionHeader {

let view = collectionView.dequeueReusableSupplementaryView(
ofKind: UICollectionElementKindSectionHeader,
withReuseIdentifier: header.viewType.typeName,
for: indexPath
)

delegate?.configure(model: header.model, view: view, indexPath: indexPath)
return view
} else if let footer = sections[indexPath.section].footer,
kind == UICollectionElementKindSectionFooter {

let view = collectionView.dequeueReusableSupplementaryView(
ofKind: UICollectionElementKindSectionFooter,
withReuseIdentifier: footer.viewType.typeName,
for: indexPath
)

delegate?.configure(model: footer.model, view: view, indexPath: indexPath)
return view
} else {
let view = DummyReusableView()
view.isHidden = true
return view
}
}

// MARK: - UICollectionViewDelegate
open func collectionView(
_ collectionView: UICollectionView,
didSelectItemAt indexPath: IndexPath) {

let item = sections[indexPath.section].items[indexPath.row]
delegate?.select(model: item.model)
collectionView.deselectItem(at: indexPath, animated: true)
}

open func collectionView(
_ collectionView: UICollectionView,
layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAt indexPath: IndexPath) -> CGSize {

let item = sections[indexPath.section].items[indexPath.row]
if let size = delegate?.size(model: item.model, containerSize: collectionView.frame.size) {
return size
}

if let size = (collectionViewLayout as? UICollectionViewFlowLayout)?.itemSize {
return size
}

return collectionView.frame.size
}

open func collectionView(
_ collectionView: UICollectionView,
layout collectionViewLayout: UICollectionViewLayout,
referenceSizeForHeaderInSection section: Int) -> CGSize {

guard let header = sections[section].header else {
return .zero
}

guard let size = delegate?.size(model: header.model, containerSize: collectionView.frame.size) else {
return .zero
}

return size
}

open func collectionView(
_ collectionView: UICollectionView,
layout collectionViewLayout: UICollectionViewLayout,
referenceSizeForFooterInSection section: Int) -> CGSize {

guard let footer = sections[section].footer else {
return .zero
}

guard let size = delegate?.size(model: footer.model, containerSize: collectionView.frame.size) else {
return .zero
}

return size
}

// MARK: - Reload
open func reload(sections: [Section]) {
// Registry
registryService.registerIfNeeded(
collectionView: collectionView,
tableView: tableView,
sections: sections
)

self.sections = sections
collectionView?.reloadData()
tableView?.reloadData()
}

// MARK: - UITableViewDataSource
open func numberOfSections(in tableView: UITableView) -> Int {
return sections.count
}

open func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return sections[section].items.count
}

open func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let item = sections[indexPath.section].items[indexPath.row]
let cell = tableView.dequeueReusableCell(
withIdentifier: item.cellType.typeName,
for: indexPath
)

delegate?.configure(model: item.model, view: cell, indexPath: indexPath)

return cell
}

// MARK: - UITableViewDelegate
open func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let item = sections[indexPath.section].items[indexPath.row]
delegate?.select(model: item.model)
tableView.deselectRow(at: indexPath, animated: true)
}

open func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
let item = sections[indexPath.section].items[indexPath.row]
if let size = delegate?.size(model: item.model, containerSize: tableView.frame.size) {
return size.height
}

return 0
}

open func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
guard let header = sections[section].header else {
return 0
}

guard let size = delegate?.size(model: header.model, containerSize: tableView.frame.size) else {
return 0
}

return size.height
}

open func tableView(_ tableView: UITableView, heightForFooterInSection section: Int) -> CGFloat {
guard let footer = sections[section].footer else {
return 0
}

guard let size = delegate?.size(model: footer.model, containerSize: tableView.frame.size) else {
return 0
}

return size.height
}

open func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
guard let header = sections[section].header else {
return nil
}

guard let view = tableView.dequeueReusableHeaderFooterView(withIdentifier: header.viewType.typeName) else {
return nil
}

delegate?.configure(model: header.model, view: view, indexPath: IndexPath(row: 0, section: section))
return view
}

open func tableView(_ tableView: UITableView, viewForFooterInSection section: Int) -> UIView? {
guard let footer = sections[section].footer else {
return nil
}

guard let view = tableView.dequeueReusableHeaderFooterView(withIdentifier: footer.viewType.typeName) else {
return nil
}

delegate?.configure(model: footer.model, view: view, indexPath: IndexPath(row: 0, section: section))
return view
}
}

Declare data

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let sections: [Section] = [
Section(
header: Header(model: Model.header("Information"), viewType: HeaderView.self),
items: [
Item(model: Model.avatar(avatarUrl), cellType: AvatarCell.self),
Item(model: Model.name("Thor"), cellType: NameCell.self),
Item(model: Model.location("Asgard"), cellType: NameCell.self)
]
),
Section(
header: Header(model: Model.header("Skills"), viewType: HeaderView.self),
items: [
Item(model: Model.skill("iOS"), cellType: SkillCell.self),
Item(model: Model.skill("Android"), cellType: SkillCell.self)
]
)
]

adapter.reload(sections: sections)

Configure required blocks

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extension ProfileViewController: AdapterDelegate {
func configure(model: Any, view: UIView, indexPath: IndexPath) {
guard let model = model as? Model else {
return
}

switch (model, view) {
case (.avatar(let string), let cell as Avatarcell):
cell.configure(string: string)
case (.name(let name), let cell as NameCell):
cell.configure(string: name)
case (.header(let string), let view as HeaderView):
view.configure(string: string)
default:
break
}
}

func select(model: Any) {
guard let model = model as? Model else {
return
}

switch model {
case .skill(let skill):
let skillController = SkillController(skill: skill)
navigationController?.pushViewController(skillController, animated: true)
default:
break
}
}

func size(model: Any, containerSize: CGSize) -> CGSize {
guard let model = model as? Model else {
return .zero
}

switch model {
case .name:
return CGSize(width: containerSize.width, height: 40)
case .avatar:
return CGSize(width: containerSize.width, height: 200)
case .header:
return CGSize(width: containerSize.width, height: 30)
default:
return .zero
}
}
}

Extending Manager

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class AccordionManager<T>: Manager<T> {
private var collapsedSections = Set<Int>()

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return collapsedSections.contains(section)
? 0 : sections[section].items.count
}

func toggle(section: Int) {
if collapsedSections.contains(section) {
collapsedSections.remove(section)
} else {
collapsedSections.insert(section)
}

let indexSet = IndexSet(integer: section)
tableView?.reloadSections(indexSet, with: .automatic)
}
}

How to take screenshots for UITest in Xcodee

Issue #539

XCUIScreenshot

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extension XCTestCase {
func takeScreenshot(name: String) {
let screenshot = XCUIScreen.main.screenshot()
let attach = XCTAttachment(screenshot: screenshot)
attach.lifetime = .keepAlways
add(attach)
}
}
Screenshot 2019-12-12 at 23 02 21

Gather screenshot for localization

xcresult from Xcode 11

xcresulttool

Test plan

How to fix UIToolbar Auto Layout issues

Issue #538

Hierarchy

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UIToolbarContentView

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_UIToolbarContentView's width should equal 0
_UIToolbarContentView's height should equal 0

Workaround that fixes 1 warning

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toolbar.setItems(items, animated: false)
toolbar.updateConstraintsIfNeeded()

###

Set frame explicitly

Use a non .zero frame that is close to the view bounds width

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let toolbar = UIToolbar(frame: CGRect(x: 0, y: 0, width: 375, height: 30))
DispatchQueue.main.async {
self.toolbar.updateConstraintsIfNeeded()
}

How to use passed launch arguments in UITests

Issue #537

Specify launch arguments

In xcodebuild, specify launch arguments.

You can specify this under Launch Arguments in Run action of the app scheme or UITest scheme

Screenshot 2019-12-10 at 23 27 02
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-AppleLanguages (jp) -AppleLocale (jp_JP)
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(lldb) po ProcessInfo().arguments
11 elements
- 0 : "/Users/khoa/Library/Developer/CoreSimulator/Devices/561F2B45-26B2-4897-98C4-8A917AEB48D2/data/Containers/Bundle/Application/436E0A43-8323-4F53-BBE0-6F75F674916F/TestAppUITests-Runner.app/TestAppUITests-Runner"
- 1 : "-AppleLanguages"
- 2 : "(ja)"
- 3 : "-AppleTextDirection"
- 4 : "NO"
- 5 : "-AppleLocale"
- 6 : "ja_JP"
- 7 : "-NSTreatUnknownArgumentsAsOpen"
- 8 : "NO"
- 9 : "-ApplePersistenceIgnoreState"
- 10 : "YES"

In UITests, pass launch arguments from UITest scheme to UITest application

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app.launchArguments += ProcessInfo().arguments

Environments

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ProcessInfo().environment // [String: String]

How to add padding to left right view in UITextField

Issue #536

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extension UITextField {
func setLeftView(_ view: UIView, padding: CGFloat) {
view.translatesAutoresizingMaskIntoConstraints = true

let outerView = UIView()
outerView.translatesAutoresizingMaskIntoConstraints = false
outerView.addSubview(view)

outerView.frame = CGRect(
origin: .zero,
size: CGSize(
width: view.frame.size.width + padding,
height: view.frame.size.height + padding
)
)

view.center = CGPoint(
x: outerView.bounds.size.width / 2,
y: outerView.bounds.size.height / 2
)

leftView = outerView
}
}

How to use decoration view in UICollectionView

Issue #529

indexPath

https://developer.apple.com/documentation/uikit/uicollectionviewlayoutattributes/1617786-layoutattributesfordecorationvie

It is up to you to decide how to use the indexPath parameter to identify a given decoration view. Typically, you use the decorationViewKind parameter to identify the type of the decoration view and the indexPath information to distinguish between different instances of that view.

Posts

How to test UserDefaults in iOS

Issue #518

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let userDefaults = UserDefaults(suiteName: suiteName)
userDefaults.removePersistentDomain(forName: suiteName)

https://developer.apple.com/documentation/foundation/userdefaults/1417339-removepersistentdomain

Calling this method is equivalent to initializing a user defaults object with init(suiteName:) passing domainName, and calling the removeObject(forKey:) method on each of its keys.

Read more

How to make Swift Package Manager package for multiple platforms

Issue #504

https://twitter.com/NeoNacho/status/1181245484867801088?s=20

There’s no way to have platform specific sources or targets today, so you’ll have to take a different approach. I would recommend wrapping all OS specific files in #if os and just having one target. For tests, you could do something similar, one test target, but conditional tests

Every files are in Sources folder, so we can use platform and version checks. For example Omnia is a Swift Package Manager that supports iOS, tvOS, watchOS, macOS and Catalyst.

For macOS only code, need to check for AppKit and Catalyst

https://github.com/onmyway133/Omnia/blob/master/Sources/macOS/ClickedCollectionView.swift

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#if canImport(AppKit) && !targetEnvironment(macCatalyst)

For SwiftUI feature, need to check for iOS 13 and macOS 10.15

https://github.com/onmyway133/Omnia/blob/master/Sources/SwiftUI/Utils/ImageLoader.swift

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@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)

How to refresh receipt and restore in app purchase in iOS

Issue #496

Read this Restoring Purchased Products to understand the purposes between the 2.

From iOS 7, every app downloaded from the store has a receipt (for downloading/buying the app) at appStoreReceiptURL. When users purchases something via In App Purchase, the content at appStoreReceiptURL is updated with purchases information. Most of the cases, you just need to refresh the receipt (at appStoreReceiptURL) so that you know which transactions users have made.

Users restore transactions to maintain access to content they’ve already purchased. For example, when they upgrade to a new phone, they don’t lose all of the items they purchased on the old phone. Include some mechanism in your app to let the user restore their purchases, such as a Restore Purchases button. Restoring purchases prompts for the user’s App Store credentials, which interrupts the flow of your app: because of this, don’t automatically restore purchases, especially not every time your app is launched.

In most cases, all your app needs to do is refresh its receipt and deliver the products in its receipt. The refreshed receipt contains a record of the user’s purchases in this app, on this device or any other device. However, some apps need to take an alternate approach for one of the following reasons:

If you use Apple-hosted content, restoring completed transactions gives your app the transaction objects it uses to download the content.
If you need to support versions of iOS earlier than iOS 7, where the app receipt isn’t available, restore completed transactions instead.

Refreshing the receipt asks the App Store for the latest copy of the receipt. Refreshing a receipt does not create any new transactions.

Restoring completed transactions creates a new transaction for every completed transaction the user made, essentially replaying history for your transaction queue observer.

More about receipt, from WWDC 2017, What’s new in StoreKit session https://developer.apple.com/videos/play/wwdc2017/303/

enter image description here

You can also watch WWDC 2017, session Advanced StoreKit for more detail https://developer.apple.com/videos/play/wwdc2017/305/

enter image description here


Original answer https://stackoverflow.com/questions/45615106/when-to-refresh-a-receipt-vs-restore-purchases-in-ios/52162283#52162283