I'm trying to dismiss a .sheet in SwiftUI, after calling an async process to confirm the user's MFA code. (I'm using the AWS Amplify Framework).
I have a binding variable set on the main view, and reference it in the view the sheet presents with #Binding var displayMFAView: Bool. I have an authentication helper that tracks the user state: #EnvironmentObject var userAuthHelper: UserAuthHelper.
The following code dismisses the sheet as expected:
func confirmMFACode(verificationCode: String) {
// Code to confifm MFA...
print("User confirmed MFA")
self.userAuthHelper.isSignedIn = true
self.displayMFAView = false
}
However, if I call the auth process via Amplify's confirmSignIn method,
func confirmVerificationMFA(verificationCode: String) {
AWSMobileClient.default().confirmSignIn(challengeResponse: verificationCode) { (signInResult, error) in
if let error = error as? AWSMobileClientError {
// ... error handling ...
} else if let signInResult = signInResult {
switch (signInResult.signInState) {
case .signedIn:
print("User confirmed MFA")
self.userAuthHelper.isSignedIn = true
self.displayMFAView = false
default:
print("\(signInResult.signInState.rawValue)")
}
}
}
}
the sheet does not get dismissed. I have tried wrapping the variable assignment in DispatchQueue.main.async {..., but that hasn't solved the issue either.
...
DispatchQueue.main.async {
self.userAuthHelper.isSignedIn = true
self.displayMFAView = false
}
...
In fact, this throws the following into my logs:
Publishing changes from background threads is not allowed; make sure to publish values from the main thread (via operators like receive(on:)) on model updates.
Wrapping the switch (... in a DispatchQueue per https://stackoverflow.com/a/58288437/217101 gave me the same warning in my log.
Admittedly I don't have a firm grasp on SwiftUI or AWS Amplify. What am I not understanding?
From what I can tell the async call does something unexpected with the state variables, but not with an EnvironmentObject. So, nstead of #Binding var displayMFAView: Bool, I stored displayMFAView in an EnvironmentObject,
#EnvironmentObject var settings: UserSettings
#State var mfaCode: String = ""
and then can show or hide the .sheet(... by updating a boolean in that object:
Button(action: {
self.signIn() // Async call happens here
self.settings.displayMFAView.toggle()
}) {
Text("Sign In")
}.sheet(isPresented: self.$settings.displayMFAView) {
// Example code to capture text
TextField("Enter your MFA code", text: self.$mfaCode)
}
Button(action: {
self.verifyMFACode(verificationCode: self.mfaCode) // async call
}) {
Text("Confirm")
}
In func verifyMFACode(), I can make an async call to validate my user, then toggle the sheet to disappear on success:
func verifyMFACode(verificationCode: String) {
AWSMobileClient.default().confirmSignIn(challengeResponse: verificationCode) {
...
case .signedIn:
self.settings.displayMFAView.toggle()
...
Related
The setup:
My app has a View ToolBar (all shortened):
struct ToolBar: View {
#State private var ownerShare: CKShare?
#State private var show_ownerModifyShare = false
// …
The toolbar has some buttons that are created by functions. One of them is
func sharingButton(imageName: String, enabled: Bool) -> SharingButton {
return SharingButton(systemImageName: imageName, enabled: enabled) {
Task {
do {
(_, participantShare, ownerShare) = try await dataSource.getSharingInfo()
// …
if ownerShare != nil { show_ownerModifyShare = true }
} catch (let error) {
//...
}
}
}
}
This is the body:
var body: some View {
HStack {
// …
sharingButton(imageName: "square.and.arrow.up", enabled: currentMode == .displayingItems)
.fullScreenCover(isPresented: $show_ownerModifyShare) {
// A CKShare record exists in the iCloud private database. Present a controller that allows to modify it.
CloudSharingView(container: CKContainer(identifier: kICloudContainerID), shareRecord: ownerShare!, dataSource: dataSource)
}
}
}
}
The problem:
When the sharingButton is tapped, ownerShare is set in Task {…}, since the iCloud database is shared as an owner.
Accordingly, show_ownerModifyShare = true is executed, and thus the body of struct ToolBar is newly rendered.
However, CloudSharingView(container: CKContainer(identifier: kICloudContainerID), shareRecord: ownerShare!, dataSource: dataSource) crashes, because ownerShare is nil, although it is only set true after ownerShare has been set != nil.
My question:
What could be the reason, and how to correct the code?
EDIT: (due to the comment of jnpdx):
I replaced .fullScreenCover(isPresented: by
.fullScreenCover(item: $ownerShare) { _ in
CloudSharingView(container: CKContainer(identifier: kICloudContainerID), shareRecord: ownerShare!, dataSource: dataSource)
}
but the code still crashes with Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value when ownerShare! is used.
You should use the item form of fullScreenCover, which allows you to send a dynamically-changed parameter to the inner closure:
.fullScreenCover(item: $ownerShare) { share in
CloudSharingView(container: CKContainer(identifier: kICloudContainerID), shareRecord: share, dataSource: dataSource)
}
This is a common issue with sheet and the related functions in SwiftUI, which calculate their closures when first rendered and not at presentation time. See related:
SwiftUI: Switch .sheet on enum, does not work
I am trying to acquaint myself with unit testing some view models in SwiftUI. The view model currently has two #Published boolean values that publish changes when an underlying UserDefaults property changes. For my unit tests, I have followed this guide on how to setup UserDefaults for testing so my production values are not modified. I am able to test the default value as such:
func testDefaultValue() {
XCTAssertFalse(viewModel.canDoThing)
}
How would I go about toggling the #Published value then ensuring my view model has received the changes? So for instance, I have a reference to my mock user defaults in my XCTestCase. I attempted to do the following with zero success:
func testValueTogglesToTrue() {
defaults.canDoThing = true
XCTAssertTrue(viewModel.canDoThing)
}
The thought being that updating the underlying user defaults value that is publishing changes to the published value in the view model will notify our view model. The above does not do anything to the view model variable. Do I need to subscribe to the publisher and use sink to accomplish this?
Let's say you store a flag in UserDefaults to know whether the user has completed onboarding:
extension UserDefaults {
#objc dynamic public var completedOnboarding: Bool {
bool(forKey: "completedOnboarding")
}
}
You have a ViewModel which tells your View whether to show onboarding or not and has a method to mark onboarding as completed:
class ViewModel: ObservableObject {
#Published private(set) var showOnboarding: Bool = true
private let userDefaults: UserDefaults
public init(userDefaults: UserDefaults) {
self.userDefaults = userDefaults
self.showOnboarding = !userDefaults.completedOnboarding
userDefaults
.publisher(for: \.completedOnboarding)
.map { !$0 }
.receive(on: RunLoop.main)
.assign(to: &$showOnboarding)
}
public func completedOnboarding() {
userDefaults.set(true, forKey: "completedOnboarding")
}
}
To test this class you have a XCTestCase:
class MyTestCase: XCTestCase {
private var userDefaults: UserDefaults!
private var cancellables = Set<AnyCancellable>()
override func setUpWithError() throws {
try super.setUpWithError()
userDefaults = try XCTUnwrap(UserDefaults(suiteName: #file))
userDefaults.removePersistentDomain(forName: #file)
}
// ...
}
Some of the test cases are synchronous for example you can easily test that showOnboarding depends on UserDefaults completedOnboarding property:
func test_whenCompletedOnboardingFalse_thenShowOnboardingTrue() {
userDefaults.set(false, forKey: "completedOnboarding")
let subject = ViewModel(userDefaults: userDefaults)
XCTAssert(subject.showOnboarding)
}
func test_whenCompletedOnboardingTrue_thenShowOnboardingFalse() {
userDefaults.set(true, forKey: "completedOnboarding")
let subject = ViewModel(userDefaults: userDefaults)
XCTAssertFalse(subject.showOnboarding)
}
Some test are asynchronous, which means you need to use XCTExpectations to wait for the #Published value to change:
func test_whenCompleteOnboardingCalled_thenShowOnboardingFalse() {
let subject = ViewModel(userDefaults: userDefaults)
// first define the expectation that showOnboarding will change to false (1)
let showOnboardingFalse = expectation(
description: "when completedOnboarding called then show onboarding is false")
// subscribe to showOnboarding publisher to know when the value changes (2)
subject
.$showOnboarding
.filter { !$0 }
.sink { _ in
// when false received fulfill the expectation (5)
showOnboardingFalse.fulfill()
}
.store(in: &cancellables)
// trigger the function that changes the value (3)
subject.completedOnboarding()
// tell the tests to wait for your expectation (4)
waitForExpectations(timeout: 0.1)
}
When creating a class conforming to ReferenceFileDocument, how do you indicate the document needs saving. i.e. the equivalent of the NSDocument's updateChangeCount method?
I've met the same problem that the SwiftUI ReferenceFileDocument cannot trigger the update. Recently, I've received feedback via the bug report and been suggested to register an undo.
Turns out the update of ReferenceFileDocument can be triggered, just like UIDocument, by registering an undo action. The difference is that the DocumentGroup explicitly implicitly setup the UndoManager via the environment.
For example,
#main
struct RefDocApp: App {
var body: some Scene {
DocumentGroup(newDocument: {
RefDocDocument()
}) { file in
ContentView(document: file.document)
}
}
}
struct ContentView: View {
#Environment(\.undoManager) var undoManager
#ObservedObject var document: RefDocDocument
var body: some View {
TextEditor(text: Binding(get: {
document.text
}, set: {
document.text = $0
undoManager?.registerUndo(withTarget: document, handler: {
print($0, "undo")
})
}))
}
}
I assume at this stage, the FileDocument is actually, on iOS side, a wrapper on top of the UIDocument, the DocumentGroup scene explicitly implicitly assign the undoManager to the environment. Therefore, the update mechanism is the same.
The ReferenceFileDocument is ObservableObject, so you can add any trackable or published property for that purpose. Here is a demo of possible approach.
import UniformTypeIdentifiers
class MyTextDocument: ReferenceFileDocument {
static var readableContentTypes: [UTType] { [UTType.plainText] }
func snapshot(contentType: UTType) throws -> String {
defer {
self.modified = false
}
return self.storage
}
#Published var modified = false
#Published var storage: String = "" {
didSet {
self.modified = true
}
}
}
ReferenceFileDocument exists for fine grained controll over the document. In comparison, a FileDocument has to obey value semantics which makes it very easy for SwiftUI to implement the undo / redo functionality as it only needs to make a copy before each mutation of the document.
As per the documentation of the related DocumentGroup initializers, the undo functionality is not provided automatically. The DocumentGroup will inject an instance of an UndoManger into the environment which we can make use of.
However an undo manager is not the only way to update the state of the document. Per this documentation AppKit and UIKit both have the updateChangeCount method on their native implementation of the UI/NSDocument object. We can reach this method by grabbing the shared document controller on macOS from within the view and finding our document. Unfortunately I don't have a simple solution for the iOS side. There is a private SwiftUI.DocumentHostingController type which holds a reference to our document, but that would require mirroring into the private type to obtain the reference to the native document, which isn't safe.
Here is a full example:
import SwiftUI
import UniformTypeIdentifiers
// DOCUMENT EXAMPLE
extension UTType {
static var exampleText: UTType {
UTType(importedAs: "com.example.plain-text")
}
}
final class MyDocument: ReferenceFileDocument {
// We add `Published` for automatic SwiftUI updates as
// `ReferenceFileDocument` refines `ObservableObject`.
#Published
var number: Int
static var readableContentTypes: [UTType] { [.exampleText] }
init(number: Int = 42) {
self.number = number
}
init(configuration: ReadConfiguration) throws {
guard
let data = configuration.file.regularFileContents,
let string = String(data: data, encoding: .utf8),
let number = Int(string)
else {
throw CocoaError(.fileReadCorruptFile)
}
self.number = number
}
func snapshot(contentType: UTType) throws -> String {
"\(number)"
}
func fileWrapper(
snapshot: String,
configuration: WriteConfiguration
) throws -> FileWrapper {
// For the sake of the example this force unwrapping is considered as safe.
let data = snapshot.data(using: .utf8)!
return FileWrapper(regularFileWithContents: data)
}
}
// APP EXAMPLE FOR MACOS
#main
struct MyApp: App {
var body: some Scene {
DocumentGroup.init(
newDocument: {
MyDocument()
},
editor: { file in
ContentView(document: file.document)
.frame(width: 400, height: 400)
}
)
}
}
struct ContentView: View {
#Environment(\.undoManager)
var _undoManager: UndoManager?
#ObservedObject
var document: MyDocument
var body: some View {
VStack {
Text(String("\(document.number)"))
Button("randomize") {
if let undoManager = _undoManager {
let currentNumber = document.number
undoManager.registerUndo(withTarget: document) { document in
document.number = currentNumber
}
}
document.number = Int.random(in: 0 ... 100)
}
Button("randomize without undo") {
document.number = Int.random(in: 0 ... 100)
// Let the system know that we edited the document, which will
// eventually trigger the auto saving process.
//
// There is no simple way to mimic this on `iOS` or `iPadOS`.
let controller = NSDocumentController.shared
if let document = controller.currentDocument {
// On `iOS / iPadOS` change the argument to `.done`.
document.updateChangeCount(.changeDone)
}
}
}
}
}
Unfortunatelly SwiftUI (v2 at this moment) does not provide a native way to mimic the same functionality, but this workaround is still doable and fairly consice.
Here is a gist where I extended the example with a custom DocumentReader view and a DocumentProxy which can be extended for common document related operations for more convenience: https://gist.github.com/DevAndArtist/eb7e8aa5e7134610c20b1a7aca358604
So I'm retrieving data from FireStore. I'm retrieving the data successfully. When I tap my search button the first time the data is being downloaded and the new view is pushed. As a result, I get a blank view. But when I go back, hit search again, sure enough I can see my data being presented.
How can I make sure I first have the data I'm searching for THEN navigate to the new view? I've used #State variables etc. But nothing seems to be working. I am using the MVVM approach.
My ViewModel:
class SearchPostsViewModel: ObservableObject {
var post: [PostModel] = []
#State var searchCompleted: Bool = false
func searchPosts(completed: #escaping() -> Void, onError: #escaping(_ errorMessage: String) -> Void) {
isLoading = true
API.Post.searchHousesForSale(propertyStatus: propertyStatus, propertyType: propertyType, location: location, noOfBathrooms: noOfBathroomsValue, noOfBedrooms: noOfBedroomsValue, price: Int(price!)) { (post) in
self.post = post
print(self.post.count)
self.isLoading = false
self.searchCompleted.toggle()
}
}
}
The code that does work, but with the bug:
NavigationLink(destination: FilterSearchResults(searchViewModel: self.searchPostsViewModel)
.onAppear(perform: {
DispatchQueue.main.async {
self.createUserRequest()
}
})
)
{
Text("Search").modifier(UploadButtonModifier())
}
Try with the following modified view model
class SearchPostsViewModel: ObservableObject {
#Published var post: [PostModel] = [] // << make both published
#Published var searchCompleted: Bool = false
func searchPosts(completed: #escaping() -> Void, onError: #escaping(_ errorMessage: String) -> Void) {
isLoading = true
API.Post.searchHousesForSale(propertyStatus: propertyStatus, propertyType: propertyType, location: location, noOfBathrooms: noOfBathroomsValue, noOfBedrooms: noOfBedroomsValue, price: Int(price!)) { (post) in
DispatchQueue.main.async {
self.post = post // << update on main queue
print(self.post.count)
self.isLoading = false
self.searchCompleted.toggle()
}
}
}
}
You should look at the Apple documentation for #State and ObservableObject
https://developer.apple.com/documentation/combine/observableobject
https://developer.apple.com/documentation/swiftui/state
Your issue is with using an #State in a non-UI class/View.
It might help if you start with the Apple SwiftUI tutorials. So you understand the differences in with the wrappers and learn how it all connects.
https://developer.apple.com/tutorials/swiftui
Also, when you post questions make sure your code can be copied and pasted onto Xcode as-is so people can test it. You will get better feedback if other developers can see what is actually happening. As you progress it won't be as easy to see issues.
Suppose I have the following ObservableObject, which generates a random String every second:
import SwiftUI
class SomeObservable: ObservableObject {
#Published var information: String = ""
init() {
Timer.scheduledTimer(
timeInterval: 1.0,
target: self,
selector: #selector(updateInformation),
userInfo: nil,
repeats: true
).fire()
}
#objc func updateInformation() {
information = String("RANDOM_INFO".shuffled().prefix(5))
}
}
And a View, which observes that:
struct SomeView: View {
#ObservedObject var observable: SomeObservable
var body: some View {
Text(observable.information)
}
}
The above will work as expected.
The View redraws itself when the ObservableObject changes:
Now for the question:
How could I do the same (say calling a function) in a "pure" struct that also observes the same ObservableObject? By "pure" I mean something that does not conform to View:
struct SomeStruct {
#ObservedObject var observable: SomeObservable
// How to call this function when "observable" changes?
func doSomethingWhenObservableChanges() {
print("Triggered!")
}
}
(It could also be a class, as long as it's able to react to the changes on the observable.)
It seems to be conceptually very easy, but I'm clearly missing something.
(Note: I'm using Xcode 11, beta 6.)
Update (for future readers) (paste in a Playground)
Here is a possible solution, based on the awesome answer provided by #Fabian:
import SwiftUI
import Combine
import PlaygroundSupport
class SomeObservable: ObservableObject {
#Published var information: String = "" // Will be automagically consumed by `Views`.
let updatePublisher = PassthroughSubject<Void, Never>() // Can be consumed by other classes / objects.
// Added here only to test the whole thing.
var someObserverClass: SomeObserverClass?
init() {
// Randomly change the information each second.
Timer.scheduledTimer(
timeInterval: 1.0,
target: self,
selector: #selector(updateInformation),
userInfo: nil,
repeats: true
).fire() }
#objc func updateInformation() {
// For testing purposes only.
if someObserverClass == nil { someObserverClass = SomeObserverClass(observable: self) }
// `Views` will detect this right away.
information = String("RANDOM_INFO".shuffled().prefix(5))
// "Manually" sending updates, so other classes / objects can be notified.
updatePublisher.send()
}
}
class SomeObserverClass {
#ObservedObject var observable: SomeObservable
// More on AnyCancellable on: apple-reference-documentation://hs-NDfw7su
var cancellable: AnyCancellable?
init(observable: SomeObservable) {
self.observable = observable
// `sink`: Attaches a subscriber with closure-based behavior.
cancellable = observable.updatePublisher
.print() // Prints all publishing events.
.sink(receiveValue: { [weak self] _ in
guard let self = self else { return }
self.doSomethingWhenObservableChanges()
})
}
func doSomethingWhenObservableChanges() {
print(observable.information)
}
}
let observable = SomeObservable()
struct SomeObserverView: View {
#ObservedObject var observable: SomeObservable
var body: some View {
Text(observable.information)
}
}
PlaygroundPage.current.setLiveView(SomeObserverView(observable: observable))
Result
(Note: it's necessary to run the app in order to check the console output.)
The old way was to use callbacks which you registered. The newer method is to use the Combine framework to create publishers for which you can registers further processing, or in this case a sink which gets called every time the source publisher sends a message. The publisher here sends nothing and so is of type <Void, Never>.
Timer publisher
To get a publisher from a timer can be done directly through Combine or creating a generic publisher through PassthroughSubject<Void, Never>(), registering for messages and sending them in the timer-callback via publisher.send(). The example has both variants.
ObjectWillChange Publisher
Every ObservableObject does have an .objectWillChange publisher for which you can register a sink the same as you do for Timer publishers. It should get called every time you call it or every time a #Published variable changes. Note however, that is being called before, and not after the change. (DispatchQueue.main.async{} inside the sink to react after the change is complete).
Registering
Every sink call creates an AnyCancellable which has to be stored, usually in the object with the same lifetime the sink should have. Once the cancellable is deconstructed (or .cancel() on it is called) the sink does not get called again.
import SwiftUI
import Combine
struct ReceiveOutsideView: View {
#if swift(>=5.3)
#StateObject var observable: SomeObservable = SomeObservable()
#else
#ObservedObject var observable: SomeObservable = SomeObservable()
#endif
var body: some View {
Text(observable.information)
.onReceive(observable.publisher) {
print("Updated from Timer.publish")
}
.onReceive(observable.updatePublisher) {
print("Updated from updateInformation()")
}
}
}
class SomeObservable: ObservableObject {
#Published var information: String = ""
var publisher: AnyPublisher<Void, Never>! = nil
init() {
publisher = Timer.publish(every: 1.0, on: RunLoop.main, in: .common).autoconnect().map{_ in
print("Updating information")
//self.information = String("RANDOM_INFO".shuffled().prefix(5))
}.eraseToAnyPublisher()
Timer.scheduledTimer(
timeInterval: 1.0,
target: self,
selector: #selector(updateInformation),
userInfo: nil,
repeats: true
).fire()
}
let updatePublisher = PassthroughSubject<Void, Never>()
#objc func updateInformation() {
information = String("RANDOM_INFO".shuffled().prefix(5))
updatePublisher.send()
}
}
class SomeClass {
#ObservedObject var observable: SomeObservable
var cancellable: AnyCancellable?
init(observable: SomeObservable) {
self.observable = observable
cancellable = observable.publisher.sink{ [weak self] in
guard let self = self else {
return
}
self.doSomethingWhenObservableChanges() // Must be a class to access self here.
}
}
// How to call this function when "observable" changes?
func doSomethingWhenObservableChanges() {
print("Triggered!")
}
}
Note here that if no sink or receiver at the end of the pipeline is registered, the value will be lost. For example creating PassthroughSubject<T, Never>, immediately sending a value and aftererwards returning the publisher makes the messages sent get lost, despite you registering a sink on that subject afterwards. The usual workaround is to wrap the subject creation and message sending inside a Deferred {} block, which only creates everything within, once a sink got registered.
A commenter notes that ReceiveOutsideView.observable is owned by ReceiveOutsideView, because observable is created inside and directly assigned. On reinitialization a new instance of observable will be created. This can be prevented by use of #StateObject instead of #ObservableObject in this instance.