Deep link onChange not triggered in SwiftUI sheet - ios

Question

I have an issue with deep links in my SwiftUI app.
In my app class I have declared deepLink as an environment variable for every View under ContentView() in the hierarchy:
...
#main
struct TestApp: App {
var userSettings: UserSettings
var dataFetcher: DataFetcher
var dataUpdater: DataUpdater
#State var deepLink = ""
init() {
userSettings = UserSettings()
dataFetcher = DataFetcher(userSettings: userSettings)
dataUpdater = DataUpdater(userSettings: userSettings)
}
var body: some Scene {
WindowGroup {
ContentView()
.environmentObject(userSettings)
.environmentObject(dataFetcher)
.environmentObject(dataUpdater)
.onOpenURL { url in
deepLink = url.absoluteString
}
.environment(\.deepLink, deepLink)
}
}
}
In my ContentView() I've declared deepLink as an environment variable
struct ContentView: View {
...
#State var isTestSheetViewPresented = false
#Environment(\.deepLink) var deepLink: String
...
var body: some View {
Button(action: {
self.isTestSheetViewPresented = true
}, label: {
HStack {
Spacer()
Image(systemName: "plus")
Text("Add")
Spacer()
}
})
.sheet(isPresented: $isTestSheetViewPresented, content: {
TestSheetView(isPresented: self.$isTestSheetViewPresented)
})
.onChange(of: self.deepLink) { _ in
self.isTestSheetViewPresented = true
}
}
}
And the TestSheetView is like this
struct TestSheetView: View {
#Environment(\.deepLink) var deepLink: String
#State var url: String = ""
var body: some View {
Text(url)
.onChange(of: deepLink) { _ in
if deepLink != "" {
self.url = deepLink
}
}
}
}
The problem is that when I click on a link, and my app opens, the TestSheetView is correctly presented but the onChange is not triggered unless I scroll a little bit down the sheet.
Instead if I put the same code of the TestSheetView in the ContentView then the text is correctly shown

Answer 1

Seems like a timing issue. While TestSheetView is being initialized, the body is created after deepLink changed, so it won't be able to detect it.
The solution is to use onAppear in TestSheetView and read from there, like so:
struct TestSheetView: View {
#Environment(\.deepLink) var deepLink: String
#State var url: String = ""
var body: some View {
Text(url)
.onAppear {
if deepLink != "" {
self.url = deepLink
}
}
}
}

Answer 2

It's unergonomic to handle both the case where the view is yet to appear, and the case where a link is being navigated within the view. The following view modifier handles both cases. It assumes an .onOpenURL() handler in the top level navigating view that sets both the current tab selection, along with the currentDeepLink environment value.
struct DeepLinkViewModifier: ViewModifier {
#Environment(\.currentDeepLink) private var currentDeepLink
let action: ((URL) -> Bool)
func body(content: Content) -> some View {
content
.onAppear {
if let url = currentDeepLink.wrappedValue,
action(url) {
currentDeepLink.wrappedValue = nil
}
}
.onOpenURL { url in
_ = action(url)
}
}
}
extension View {
func onDeepLink(perform action: #escaping ((URL) -> Bool)) -> some View {
return self.modifier(DeepLinkViewModifier(action: action))
}
}
Use:
struct SomeView: View {
#State urlString: String = ""
var body: some View {
Text(urlString).onDeepLink { url
self.string = url.absoluteString
return true // return false if another handler should consume
}
}
}
struct ContentView: View {
#State private var tabSelection: TabSelection = .something
#State private var currentDeepLink: URL? = nil
var body: some View {
TabView(selection: self.$tabSelection) {
...
}
.onOpenURL { url in
self.tabSelection = ... // determine selection from URL
self.currentDeepLink = url
}
.environment(\.tabSelection, self.$tabSelection)
.environment(\.currentDeepLink, self.$currentDeepLink)
}
}