Using Async Await in Unity

Question

I am trying to make a reload mechanism in Unity, but the function is in a scriptable object. This means I cannot use Coroutine as it is in MonoBehaviour. I could think of solving with a simple timer with Time.time and Time.deltaTime but for that, I should call the function every frame which seems not too right for me, I'd like to avoid this solution.

I thought about using C#'s built-in Async Await functions but I never used it before and it's quite confusing, I have no idea how to implement it after looking at Microsoft's documentation. I've tried implementing it but I always get an error saying

The body of 'Weapon.Reload()' cannot be an iterator block because 'void' is not an iterator interface type

I've done a coroutine implementation so it's easier to see what I want to achieve using Async/Await.

public virtual IEnumerator Reload()
{
    if (currentMagazine == magazineSize)
        yield break;

    if (!reloading)
    {
        Debug.Log("Started reloading");
        reloading = true;
    } 
    else 
    {
        yield return new WaitForSeconds(reloadTime);
        currentMagazine = magazineSize;
        reloading = false;
        Debug.Log("Reload time over");
    }

    Debug.Log("Finished reloading");
    yield break;
}

I want to be able to call this function and just let it do its job over time, without stopping code execution. At first, I tried the simple timer solution with a while loop then realized that just stops code execution so it's not working properly.

How could I do this using C#'s Async/Await?

Answer 1

You can have a coroutine runner MonoBehaviour that runs coroutines defined elsewhere. For example:

public class CoroutineRunner : MonoBehaviour {
  private static CoroutineRunner instance;
  public static void RunCoroutine(IEnumerator coroutine) {
    if (instance == null) {
      instance = new GameObject("runner").AddComponent<CoroutineRunner>();
    }
    instance.StartCoroutine(coroutine);
  }
}

And to use it:

CoroutineRunner.RunCoroutine(Reload());

I know this doesn’t answer your question, but it does solve your problem by challenging your assumption that you cannot use coroutines in a scriptable object (or anywhere you want).

Answer 2

public virtual async void Reload()
{
    if (currentMagazine == magazineSize)
        return;

    if (!reloading)
    {
        Debug.Log("Started reloading");
        reloading = true;
    } 
    else 
    {
        await Task.Delay(reloadTime * 1000);
        currentMagazine = magazineSize;
        reloading = false;
        Debug.Log("Reload time over");
    }

    Debug.Log("Finished reloading");
}

To call, just use Reload().