An example function:
#ViewBuilder func returnView() -> some View {
if thisIsTrue == true {
SomeView()
} else {
AnotherView()
}
}
I've tried testing like this:
let testView = sut.returnView()
XCTAssert(testView is SomeView)
Which passes when there is only one possible type of view, but then fails as soon as there is a choice.
Any suggestions as to how I can unit test the output of this function?
The opaque return type some View means this function always returns exactly one type on all paths our of the function and that type conforms to View, so while it looks like you are returning two different things the ViewBuilder in fact collapses this into a single type that is generic with respect to the real return type. If you want to know what the opaque type really is you can just have the compiler tell you. For instance here is a playground. Note that this solution is fragile because changing the implementation of the function very likely will change the return type.
import SwiftUI
struct SomeView: View {
var body: some View { EmptyView() }
}
struct AnotherView: View {
var body: some View { Color.red}
}
#ViewBuilder func returnView() -> some View {
if true {
SomeView()
} else {
AnotherView()
}
}
let a = returnView()
print(type(of: a))
output:
_ConditionalContent<SomeView, AnotherView>
The solution that I went with was to not unit test the output of the function at all.
I created an enum in the view model that had cases that mapped to the different views and then used a computed property of this type to separate the business logic from the view logic.
enum ViewType {
case someView
case anotherView
}
var viewType: ViewType {
if thisIsTrue {
return .someView
} else {
return .anotherView
}
}
I can instantiate and test this in my unit testing.
Then in the view itself I created an #ViewBuilder variable and used a switch statement to map it to the view model viewType:
#ViewBuilder var view: some View {
switch viewModel.viewType {
case .someView:
SomeView()
case .anotherView:
AnotherView()
}
}
I hope this is helpful to someone else.
Related
I have a fairly complex document type to work with. It is basically a bundle containing a set of independent documents of the same type, with various pieces of metadata about the documents. The data structure that represents the bundle is an array of structs, similar to this (there are several more fields, but these are representative):
struct DocumentData: Equatable, Identifiable, Hashable {
let id = UUID()
var docData: DocumentDataClass
var docName: String
var docFileWrapper: FileWrapper?
func hash(into hasher: inout Hasher) {
id.hash(into: &hasher)
}
static func ==(lhs: KeyboardLayoutData, rhs: KeyboardLayoutData) -> Bool {
return lhs.id == rhs.id
}
}
The window for the bundle is a master-detail, with a list on the left and, when one is selected, there is an edit pane for the document on the right. The FileWrapper is used to keep track of which files need to be written for saving, so it gets initialised on reading the relevant file, and reset when an undoable change is made. That is largely the only way that the DocumentData structure gets changed (ignoring explicit things like changing the name).
I've reached a point where a lot of things are working, but I'm stuck on one. There's a view inside the edit pane, several levels deep, and when I double-click it, I want a sheet to appear. It does so, but then disappears by itself.
Searching for ways to work this out, I discovered by using print(Self._printChanges()) at various points that the edit pane was being refreshed after showing the sheet, which meant that the parent disappeared. What I found was that the dependency that changed was the DocumentData instance. But, I then added a print of the DocumentData instance before the _printChanges call, and it is identical. I have also put in didSet for each field of DocumentData to print when they get set, and nothing gets printed, so I'm not sure where the change is happening.
So the question comes down to how I can work out what is actually driving the refresh, since what is claimed to be different is identical in every field.
There are some other weird things happening, such as dragging and dropping text into the view causing the whole top-level document array of DocumentData items to change before the drop gets processed and the data structures get updated, so there are things I am not understanding as clearly as I might like. Any guidance is much appreciated.
ADDED:
The view that triggers the sheet is fairly straightforward, especially compared to its enclosing view, which is where most of the interface code is. This is a slightly simplified version of it:
struct MyView: View, DropDelegate {
#EnvironmentObject var keyboardStatus: KeyboardStatus
#Environment(\.displayFont) var displayFont
#Environment(\.undoManager) var undoManager
var keyCode: Int
#State var modifiers: NSEvent.ModifierFlags = []
#State private var dragHighlight = false
#State private var activeSheet: ActiveSheet?
#State private var editPopoverIsPresented = false
// State variables for double click and drop handling
...
static let dropTypes = [UTType.utf8PlainText]
var body: some View {
ZStack {
BackgroundView(...)
Text(...)
}
.onAppear {
modifiers = keyboardStatus.currentModifiers
}
.focusable(false)
.allowsHitTesting(true)
.contentShape(geometry.contentPath)
.onHover { entered in
// updates an inspector view
}
.onTapGesture(count: 2) {
interactionType = .doubleClick
activeSheet = .doubleClick
}
.onTapGesture(count: 1) {
handleItemClick()
}
.sheet(item: $activeSheet, onDismiss: handleSheetReturn) { item in
switch item {
case .doubleClick:
DoubleClickItem(...) ) {
activeSheet = nil
}
case .drop:
DropItem(...) {
activeSheet = nil
}
}
}
.popover(isPresented: $editPopoverIsPresented) {
EditPopup(...)
}
.onDrop(of: KeyCap.dropTypes, delegate: self)
.contextMenu {
ItemContextMenu(...)
}
}
func handleItemClick() {
NotificationCenter.default.post(name: .itemClick, object: nil, userInfo: [...])
}
func handleEvent(event: KeyEvent) {
if event.eventKind == .dropText {
interactionType = .drop
activeSheet = .drop
}
else if event.eventKind == .replaceText {
...
handleItemDoubleClick()
}
}
func handleSheetReturn() {
switch interactionType {
case .doubleClick:
handleItemDoubleClick()
case .drop:
handleItemDrop()
case .none:
break
}
}
func handleItemDoubleClick() {
switch itemAction {
case .state1:
...
case .state2:
...
case .none:
// User cancelled
break
}
interactionType = nil
}
func handleItemDrop() {
switch itemDropAction {
case .action1:
...
case .action2:
...
case .none:
// User cancelled
break
}
interactionType = nil
}
// Drop delegate
func dropEntered(info: DropInfo) {
dragHighlight = true
}
func dropExited(info: DropInfo) {
dragHighlight = false
}
func performDrop(info: DropInfo) -> Bool {
if let item = info.itemProviders(for: MyView.dropTypes).first {
item.loadItem(forTypeIdentifier: UTType.utf8PlainText.identifier, options: nil) { (textData, error) in
if let textData = String(data: textData as! Data, encoding: .utf8) {
let event = ...
handleEvent(event: event)
}
}
return true
}
return false
}
}
Further edit:
I ended up rewiring the code so that the sheet belongs to the higher level view, which makes everything work without solving the question. I still don't understand why I get a notification that a dependency has changed when it is identical to what it was before, and none of the struct's didSet blocks are called.
Try removing the class from the DocumentData. The use of objects in SwiftUI can cause these kind of bugs since it’s all designed for value types.
Try using ReferenceFileDocument to work with your model object instead of FileDocument which is designed for a model of value types.
Try using sheet(item:onDismiss:content:) for editing. I've seen people have the problem you describe when they try to hack the boolean sheet to work with editing an item.
To provide some context, Im writing an order tracking section of our app, which reloads the order status from the server every so-often. The UI on-screen is developed in SwiftUI. I require an optional image on screen that changes as the order progresses through the statuses.
When I try the following everything works...
My viewModel is an ObservableObject:
internal class MyAccountOrderViewModel: ObservableObject {
This has a published property:
#Published internal var graphicURL: URL = Bundle.main.url(forResource: "tracking_STAGEONE", withExtension: "gif")!
In SwiftUI use the property as follows:
GIFViewer(imageURL: $viewModel.graphicURL)
My issue is that the graphicURL property has a potentially incorrect placeholder value, and my requirements were that it was optional. Changing the published property to: #Published internal var graphicURL: URL? causes an issue for my GIFViewer which rightly does not accept an optional URL:
Cannot convert value of type 'Binding<URL?>' to expected argument type 'Binding<URL>'
Attempting the obvious unwrapping of graphicURL produces this error:
Cannot force unwrap value of non-optional type 'Binding<URL?>'
What is the right way to make this work? I don't want to have to put a value in the property, and check if the property equals placeholder value (Ie treat that as if it was nil), or assume the property is always non-nil and unsafely force unwrap it somehow.
Below is an extension of Binding you can use to convert a type like Binding<Int?> to Binding<Int>?. In your case, it would be URL instead of Int, but this extension is generic so will work with any Binding:
extension Binding {
func optionalBinding<T>() -> Binding<T>? where T? == Value {
if let wrappedValue = wrappedValue {
return Binding<T>(
get: { wrappedValue },
set: { self.wrappedValue = $0 }
)
} else {
return nil
}
}
}
With example view:
struct ContentView: View {
#StateObject private var model = MyModel()
var body: some View {
VStack(spacing: 30) {
Button("Toggle if nil") {
if model.counter == nil {
model.counter = 0
} else {
model.counter = nil
}
}
if let binding = $model.counter.optionalBinding() {
Stepper(String(binding.wrappedValue), value: binding)
} else {
Text("Counter is nil")
}
}
}
}
class MyModel: ObservableObject {
#Published var counter: Int?
}
Result:
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
Some of the UI setups not working automatically with the Dark/Light mode change as the UIColor. For example shadow in layer. As I need to remove and drop shadow in dark and light mode, I need somewhere to put updateShadowIfNeeded() function. I know how to detect what is the mode currently:
func dropShadowIfNeeded() {
switch traitCollection.userInterfaceStyle {
case .dark: removeShadow()
case .light: dropShadowIfNotDroppedYet()
default: assertionFailure("Unknown userInterfaceStyle")
}
}
Now I put the function inside the layoutSubviews, since it gets called every time appearance change:
override func layoutSubviews() {
super.layoutSubviews()
dropShadowIfNeeded()
}
But this function is getting called A LOT. What is the proper function to trigger only if userInterfaceStyle changed?
SwiftUI
With a simple environment variable on the \.colorScheme key:
struct ContentView: View {
#Environment(\.colorScheme) var colorScheme
var body: some View {
Text(colorScheme == .dark ? "Its Dark" : "Its. not dark! (Light)")
}
}
UIKit
As it described in WWDC 2019 - Session 214 around 23:30.
As I expected, this function is getting called a lot including when colors changing. Along side with many other functions for ViewController and presentationController. But there is some especial function designed for that has a similar signature in all View representers.
Take a look at this image from that session:
Gray: Calling but not good for my issue, Green: Designed for this
So I should call it and check it inside this function:
override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
super.traitCollectionDidChange(previousTraitCollection)
if traitCollection.hasDifferentColorAppearance(comparedTo: previousTraitCollection) {
dropShadowIfNeeded()
}
}
This will guarantee to be called just once per change.
if you are only looking for the initial state of the style, check out this answer here
I think this should get called significantly less often, plus the guard makes sure you only react to user interface style changes:
override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
super.traitCollectionDidChange(previousTraitCollection)
guard previousTraitCollection?.userInterfaceStyle != traitCollection.userInterfaceStyle else {
return
}
dropShadowIfNeeded()
}
With RxSwift and ObjectiveC runtime, you can achieve it without inheritance
here is the encapsulated version:
import UIKit
import RxSwift
import RxCocoa
enum SystemTheme {
static func get(on view: UIView) -> UIUserInterfaceStyle {
view.traitCollection.userInterfaceStyle
}
static func observe(on view: UIView) -> Observable<UIUserInterfaceStyle> {
view.rx.methodInvoked(#selector(UIView.traitCollectionDidChange(_:)))
.map { _ in SystemTheme.get(on: view) }
.distinctUntilChanged()
}
}
I'm trying to create a list from an array of Request objects.
I have defined a custom view RequestRow to display a Request.
The following works to display a list of requests…
struct RequestsView : View {
let requests: [Request]
var body: some View {
List {
ForEach(0..<requests.count) { i in
RequestRow(request: self.requests[i])
}
}
}
}
but the following won't compile…
struct RequestsView : View {
let requests: [Request]
var body: some View {
List {
ForEach(requests) { request in
RequestRow(request: request)
}
}
}
}
Cannot convert value of type '(Request) -> RequestRow' to expected argument type '(_) -> _'
Any thoughts as to what the issue might be?
OK, I soon figured out the answer. Per the Apple's docs, the array elements must be Identifiable, so this works…
var body: some View {
List {
ForEach(requests.identified(by: \.self)) { request in
RequestRow(request: request)
}
}
}
I'm sure I won't be the last person to have this problem, so I'll leave this here for future reference.
I have the same problem, but in my case Component is a Protocol, so it can't be conformed to Identifiable
VStack {
ForEach(components.identified(by: \.uuid)) { value -> UIFactory in
UIFactory(component: value)
}
}
However, If I try something like this it works fine
VStack {
ForEach(components.identified(by: \.uuid)) { value -> UIFactory in
Text(value.uuid)
}
}