SwiftUI view task and async function

Question

I'm getting a warning with this code and I don't understand how to fix it. I'm curious to know how to pass a function into the task modifier.

private func placeholderRHSView(for client: AppClient) -> some View {
    Color.clear
        .frame(width: 290, height: 290)
        .task(load(client)) // Warning: Converting non-sendable function value to '@Sendable () async -> Void' may introduce data races
}

private func load(_ client: AppClient) -> () -> Void {
    return {
        Task {
            do {
                let apps = try await client.recent()
            } catch {}
        }
    }
}

How should I re-structure this code to make it thread safe?

lorem ipsum · Accepted Answer · 2023-02-05 14:43:03Z

First issue is having that floating Task {/*code*/} that isn't thread safe and should not be used without a very good reason and precautions that mimic .task lifecycle behavior.

Now to get a function that can be used directly in .task we have to mimic the signature

func task(priority: TaskPriority = .userInitiated, _ action: @escaping () async -> Void) -> some View

The action is () async -> Void so the function should return that exact type. You are missing the async part.

You also have to add @Sendable which we only know about from warnings

private func load(_ client: AppClient) -> (@Sendable () async -> Void) {

() means that this will be a closure/function so the body will be enclosed with return {/*async code here*/}

private func load(_ client: AppClient) -> (@Sendable () async -> Void) {
   return {
        do {
            let apps = try await client.recent()
            print(apps)
        } catch {
            print(error)
        }
    }
}

Now your View will work as expected.

private func placeholderRHSView(for client: AppClient) -> some View {
    Color.clear
        .frame(width: 290, height: 290)
        .task(load(client))
}

I created a little mock AppClient to make this complie.

struct AppClient{
    func recent() async throws -> String{
        return "recent"
    }
}

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