1

Hey, I have a question about Sendable. I'm not sure if this is too SwiftUI-specific.

According to Apple's documentation, @State is thread safe. But it is not Sendable. I'm not sure I understand the difference between those two concepts. Shouldn't something that's thread safe also be Sendable? Or am I missing something?

The reason I'm asking is because I have a custom property wrapper that contains a @State, but with full Concurrency checking enabled, I get a warning every time I try to pass an instance of it into a Task:

@propertyWrapper
struct MyType: DynamicProperty {
    @State var isActive: Bool? = nil

    public var wrappedValue: Self {
        self
    }

}

struct MyContentView: View {
    @MyType var testState

    var body: some View {
        Text("A")
    }

    func test() {
        Task {
           // Warning: Capture of 'self' with non-sendable type 'MyContentView' in a `@Sendable` closure 
           let tes1t = testState
        }
    }
}

Would it be safe to mark MyType as @unchecked Sendable? Or does this depend on internal implementation logic of @State, which only Apple has?

Thanks for any help! :)

2

Property wrappers can't currently conform to Sendable properly, the compiler doesn't add the conformance to the synthesized internal properties, like _wrappedValue. I'm also not sure it would play well with DynamicProperty either. In general, you really don't want to perform async work from your SwiftUI views.

3

Ah okay, that makes sense.

Thank you :)