How to call async-wait method in any function by using callback-CodePudding

I am using UniTask in Unity 2020.3. And I want to call an async method which returns a UniTask in Unity Event Function.

For some reason, I cannot change the event function to async version, is there any other way to call it?

Such as, wrap the async method into a callback function?

For example, I have an async function like this:

public void async UniTask<string> GetStringAsync();

And I want to call it like below:

public class MyMonoBehaviour: MonoBehaviour
{
   pirvate string myString;


   pirvate void Start()
   {
       myString = await GetStringAsync();
   }
}

I cannot use await in Start() because it is not an async function. So, I want to wrap GetStringAsync() into a callback function and call it in Start(), but I have no idea how to do it.

I know the simplest solution is to change Start() to async Start(),

But what if I want to call GetStringAsync() in any normal function? Change it to async again? I dislike the async spread in my code base like virus. Because the function may be some legacy code, I want to modify it as little as possible.

CodePudding user response：

I would solve this by changing the signature to async void Start(). That works. If you need Update to be delayed until Start finishes, change Start to a coroutine and use UniTask's API for creating an iterator from a task (which you will yield).

Note: I don't use the UniTask library, but it seems pretty equivalent to Async Await Utils. Both provide the GetAwaiter() extension method for common Unity types. There is certainly some function that lets a coroutine wait for a task (by wrapping it in an IEnumerator).

CodePudding user response：

I found the solution I wanted for myself.

I create a wrapper function like below:

public void async UniTask<string> GetStringCallbackAsync(Action<string> onDone) {
    string result = await GetStringAsync();
    onDone(result);
}

And I can call it in any function like below:

GetStringCallbackAsync(result => {
   Debug.log($"result = {result}");
}
).Forget();

Maybe I didn't describe my question clearly, but this is the result I wanted.