IsDone Coroutine Example

using System;
using System.Collections;
using UnityEngine;

public class AdvancedCoroutines : MonoBehaviour
{
    IEnumerator Start()
    {
        var isDone = new IsDoneObject();
        StartCoroutine(MyActions.DelayedAction(1, () => print("HUZZAH!"), timeRemaining => print(timeRemaining), isDone));
        while (!isDone) yield return null;
        print("Finished");
    }
}

public static class MyActions
{
    public static IEnumerator DelayedAction(float delayTime, Action action, Action<float> timeRemaingUpdate = null, IsDoneObject isDone = null)
    {
        while (delayTime > 0)
        {
            if (timeRemaingUpdate != null) timeRemaingUpdate(delayTime -= Time.deltaTime);
            yield return null;
        }

        action();
        if (isDone != null) isDone.SetDone();
    }
}

public class IsDoneObject
{
    private bool isDone = false;

    public void SetDone()
    {
        isDone = true;
    }

    public static implicit operator bool(IsDoneObject x)
    {
        return x.isDone;
    }
}