如何等待协程回调执行？

Question

我想等待StartCoroutine回调执行。有人知道该怎么做吗？

public float getXXX() {

  var result;

  StartCoroutine(YYY((r) => result = r)); // how to wait this?

  return result;

}

private IEnumerator YYY(System.Action<float> callback) {

  LinkedList<float> list = new LinkedList<float>();

  while(timeleft > 0) {

    timeleft -= Time.deltaTime;

    list.add(transform.position.magnitude);

    yield return new WaitForSeconds (WAITSPAN);

  }

  callback(list.max());

  yeild return true;

}