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Xcode – Swift Error with existing codebase: Main actor-isolated context may introduce data races

OK, all of a sudden I’m getting warnings (and runtime errors) in code that hasn’t changed in quite some time. I believe this has to do with Swift concurrency.

Further details below. All help appreciated greatly. On where to look next.

Using the example code from Apple also shows this issue.
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I’m getting errors using the new environment variables to open an existing document: Apple Developer Link

I get this error when I have my swiftui View as being @MainActor:
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I get this error without it:
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I get this if I set the Task to run on the Main Actor
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Run time crash:
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And console output on runtime crash:
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Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    Thank you @Lorem Ipsum and @malhal for trying to help and not just down voting.

    For others having similar issues the answer was to do as Lorem ipsum suggested to make the parent view @MainActor, but also to pull the code out of the view body and into it's own method and call that async method from a Task call within the view body.

    In my code I am declaring the Environment variable within the view as before but have moved the call to it to a function inside the View:

    @MainActor struct ExistingProjectButton: View {
    @Environment(.openDocument) private var openDocument

var body: some View {
...
.simultaneousGesture(TapGesture(count: 2).onEnded {
    Task{
        await openExistingDocument(url: buttonURL)
    }
}


func openExistingDocument(url: URL) async{
        do {
            try await openDocument(at: url)
        } catch {
            // Handle error
            print("Error opening: (error.localizedDescription)")
        }
    }
}

  2. 0

    It’s .task in SwiftUI not Task. In your case probably something like:

    .onGesture {
    count += 1
}
.task(id: count) {

}
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