OnBecameInvisible can be a Co-routine?

While reading Unity's documentation today I saw this

at http://docs.unity3d.com/ScriptReference/MonoBehaviour.OnBecameInvisible.html

But I have no idea of a situation where it'd be necessary to use it as a co-routine. How would it even work?

 

Code (CSharp):

1. IEnumerator isStarted;
2. IEnumerator OnBecameInvisible()
3. {
4.     isStarted = new WaitForSeconds(4f);
5.     yield return isStarted;
6.     gameObject.SetActive(false);
7. }
8. void OnBecameVisible()
9. {
10.     if(isStarted!=null)
11.     {
12.         StopCoroutine(isStarted);
13.         isStarted=null;
14.     }
15. }
16.  

Will disable object if it was invisible for 4 seconds or more, but won't disable it if it is visible at least once per 4 seconds. Good for things you want to despawn when they're off screen for long.

In general, you could use it for any delayed action (do something after X time passed or on next frame).

P.S. Start() can be coroutine too.

 

most of the unity messages a MonoBehaviour can receive can all be made coroutines, and unity will automatically run them as such. With some exceptions (like Awake).

This is just as a short cut, so that you don't have to start the coroutine yourself (which would make you have 2 methods, instead of 1).

Code (csharp):

1.  
2. function OnBecameInvisible()
3. {
4.     StartCoroutine(SomeRoutine());
5. }
6.  
7. function SomeRoutine()
8. {
9.     //do stuff
10.  
11.     yield WaitForSeconds(1f);
12.  
13.     //do stuff
14. }
15.  
16. //vs
17.  
18. function OnBecameInvisible()
19. {
20.     //do stuff
21.  
22.     yield WaitForSeconds(1f);
23.  
24.     //do stuff
25. }
26.  

In this example, what if 'OnBecameInvisible' you wanted to wait a second. You can.

Who knows what you'll want to do. The possibilities are infinite.

 

Thanks Teravisor and lordofduct!
That really opened up a lot of possibilities for me.