Unity3D extension method for being able to call an array of async code blocks in sequence.

RunAsyncSequence.cs

public delegate float SequenceFunc();

public static void RunAsyncSequence(this MonoBehaviour obj, params SequenceFunc[] callbacks)
{
   if (callbacks.Length > 0) {
      obj.StartCoroutine(ExecFuncChain(callbacks));
   }
}

private static IEnumerator ExecFuncChain(SequenceFunc[] callbacks)
{
   // exec all but the last
   for (int i = 0; i < callbacks.Length-1; ++i) {
      yield return new WaitForSeconds(callbacks[i]());
   }
   // last is special case, just execute it and don't wait around
   callbacks[callbacks.Length - 1]();
   yield return new WaitForEndOfFrame();
}

// Usage:
this.RunAsyncSequence(
   () => {
      // Do async stuff and then call the next after 2 seconds
      return 2;
   },
   () => {
      // Do more stuff and then call the next after 3 seconds
      return 3;
   },
   () => {
      // Do final stuff
      return 0;
   }
);