How to pass "ref parameter" in iterator method?

Question

Hi all,
I need to pass a "ref" parameter to a IEnumerator method, but I sadly found out that it's not possible to use "ref" as a parameter in a iterator...here's my code below, which of course throws an error:

public class CountDownTimer : MonoBehaviour {

 public static IEnumerator CountDown (string objName, string displayEndText, float timer, ref bool boolToPass) {

     // Create a new GameObject for the countdown timer and child it to "HUD"
     GameObject countDownGO = new GameObject(objName);
     countDownGO.transform.parent = GameObject.Find("HUD").transform;

     // Create the GUIText component which displays the countdown and attach it to the countDownGO gameObject created above
     GUIText countText = countDownGO.AddComponent&lt;GUIText&gt;();
     countText.text = timer.ToString();
     countText.font = (Font)Resources.Load("Fonts/Arial Black", typeof(Font));
     countText.material = countText.font.material;
     countText.anchor = TextAnchor.MiddleCenter;
     countText.alignment = TextAlignment.Center;
     countText.transform.position = new Vector3 (0.5f,0.5f,0.0f);
     countText.lineSpacing = 1;
     countText.tabSize = 0;

     yield return new WaitForSeconds (1.0f); // Wait 1 second before starting the timer

     // While the timer is bigger then 1, decrease it every seconds and round the number to an int
     while (timer &gt; 1) {

         timer -= Time.deltaTime;
         countText.text = Mathf.Round(timer).ToString();

         // When timer reaches 1, wait 0.5 seconds, then display end text and call callback function, wait 1 second then destroy the gameObject
         if (timer &lt;= 1) {

             yield return new WaitForSeconds (0.5f);
             countText.text = displayEndText;
             boolToPass = true;

             yield return new WaitForSeconds (1.0f);
             Destroy(countDownGO);
             break;

         }

         yield return null;

     }

 } // End of CountDown IEnumerator function

I have looked around and found a few solutions, but I'm having a hard time understanding them and I haven't been able to successfully apply them to my own code. Could anyone show me how to do this with my code above?

Thanks a lot!
Stephane

Answer 1

How about using a delegate? I don't know in for what special case you need this bool but with a delegate you can pass a callback routine.

public delegate void OnTimerExpired();

public static IEnumerator CountDown (string objName, string displayEndText, float timer, OnTimerExpired callback) {

[...]

 if (timer &lt;= 1)
 {
     yield return new WaitForSeconds (0.5f);
     countText.text = displayEndText;
     if (callback != null)
         callback();

[...] }

void MyCallback() { // Timer expired }

// To start the coroutine use: StartCoroutine(CountDown("...", "...", 5, MyCallback));

edit

You can also pass an object to your coroutine. Classes are always reference types. Just create a class that holds the data you want to return.

public class CCoroutineResult
{
    public bool MyBool = false;
}

Define your coroutine like:

public static IEnumerator CountDown (string objName, string displayEndText, float timer, CCoroutineResult result)

You can easily change the bool inside your coroutine with: result.MyBool = true;

second edit
Well, just realised what you are doing inside your coroutine. You could go for another approach. StartCoroutine is a method of MonoBehaviour and the coroutine that is started is bound to the MonoBehaviour object. Since your function creates a temp GO you could run the coroutine on that gameobject. Just use a static method as a kind of constructor and remove the static from your coroutine. Create the GameObject within your static method and return the script instance.

public class CountDownTimer : MonoBehaviour
{
    public string displayEndText;
    public float timer;
    bool Done = false;
    private IEnumerator CountDown ()
    {
        // Here you can do all your stuff on the actual GameObject.
        // Just refer to `gameObject`
        [...]
    }
    public static CountDownTimer CreateTimer(float aDuration, string aEndText)
    {
        // Create a new GameObject for the countdown timer and child it to "HUD"
        GameObject countDownGO = new GameObject(objName);
        CountDownTimer CDScript = countDownGO.AddComponent< CountDownTimer >();
        CDScript.timer = aDuration;
        CDScript.displayEndText = aEndText;
        CDScript.StartCoroutine(CountDown());
        return CDScript;
    }
}

How to pass "ref parameter" in iterator method?

modern solution here ...

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