Update () cant be a coroutine

Question

I´m making a script that loads a level after collecting certain amount of pages like slender.... here is the FULL script;

 #pragma strict
 @script RequireComponent ( AudioSource )
 var papers : int = 0;
 var papersToWin = 8;
 var distanceToPaper : float = 2.5;
 public var paperPickup : AudioClip;
 
 function Start () 
 {
     Screen.lockCursor = true;
 }
 
 function Update () 
 {
     if(Input.GetMouseButtonDown (0) || Input.GetKeyDown (KeyCode.E))
     {
     var ray = Camera.main.ScreenPointToRay(Vector3(Screen.width * 0.5, Screen.height * 0.5, 0.0));
     var $$anonymous$$t : RaycastHit;
     
     if(Physics.Raycast(ray, $$anonymous$$t, distanceToPaper))
     {
     
     if($$anonymous$$t.collider.gameObject.name == "Paper")
     {
      papers += 1;
      audio.PlayClipAtPoint(paperPickup, transform.position);
      Destroy($$anonymous$$t.collider.gameObject);
      
      if( papers < papersToWin)
          yield WaitForSeconds(3);
          Application.LoadLevel("next");
     }
     }
     }
 }
 
 function OnGUI ()
 {
     if(papers < papersToWin)
     {
     GUI.Box(Rect((Screen.width * 0.5) -60, 10, 120, 25),  papers.ToString() + " of " + papersToWin.ToString() + " Pages");
     }
     else
     GUI.Box(Rect((Screen.width/2) - 100, 10, 200, 35), "You Won!");
 }

Answer 1

Unity is right: Update can't be a coroutine. You can call a coroutine from Update, or use a "CoUpdate" coroutine instead:

 function Start(): IEnumerator { // turn Start into a coroutine
   w$$anonymous$$le (true){// create an eternal loop
     yield CoUpdate(); // call CoUpdate each frame
   }
 }

 function CoUpdate(): IEnumerator { // CoUpdate is called every frame
   if (papers < papersToWin){
     yield WaitForSeconds(3); // CoUpdate can WaitForSeconds!
     Application.LoadLevel("next");
   }
 }

If you want to use Update, write a separate coroutine and make sure it's not called again w$$anonymous$$le executing! : each time you call a coroutine, a new instance of it is created and starts running, thus in a few seconds you may have lots of coroutines executing in parallel:

 var running = false; // tells whether LoadNext is running

 function LoadNext(): IEnumerator {
   running = true; // LoadNext started
   WaitForSeconds(3);
   Application.LoadLevel("next");
   running = false; // LoadNext ended (unnecessary, since t$$anonymous$$s level has finished) 
 }
  
 function Update(){
   if (!running && papers < papersToWin){
     LoadNext(); // only call LoadNext if it's not already running
   }
 }

Answer 2

Answer by Lovrenc · Aug 04, 2013 at 03:50 PM

Update is reserved name for function in unity. Update gets called in a loop by game engine. Therefore you cannot use

 yield WaitForSeconds(3);

in Update function. Write separate function for that.

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Update () cant be a coroutine

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