How to use a WHILE LOOP? Obviously not inside function Update

Question

I used a while loop as follows:

//while myBoolean is true, I want the gameObject's tag to become "HotObject" (and 
//obviously when myBoolean turns false, the tag will be reverted back to what it was).
function Update () {
        while (myBoolean)   {
        gameObject.tag="HotObject";
        }   
}

As many of you must have already guessed, this freezes Unity. I searched for relevant questions a bit and I learned that while loops inside function Update freeze Unity. So how would I use the aformentioned loop? (and a happy 2011 everybody!)

Answer 1

Best Answer

Answer by Ejlersen · Dec 31, 2010 at 05:56 PM

Okay, lets take a look at the while-loop:

while(condition)
{
    code
}

A while-loop keeps executing its code, while its condition is true. E.g.

var i : int = 0;

while (i < 10)
{
    Debug.Log("Index i is: " + i);

 i++;

This will print:

Index i is: 0

Index i is: 1

Index i is: 2

Index i is: 3

Index i is: 4

Index i is: 5

Index i is: 6

Index i is: 7

Index i is: 8

Index i is: 9

It stops there, because i = 10 does not satisfy the condition: i < 10.

You can also do this with an for-loop, e.g.:

for (var i : int = 0; i < 10; i++)
{
    Debug.Log("Index i is: " + i);
}

A while loop in Update() does not make the program "freeze", but given the condition you gave the while-loop will make it loop forever, until its condition is false.

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schwertfisch · Dec 31, 2010 at 06:46 PM 1

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I believe you mean that the while loop does not necessarily freeze the program if inside Update and whether it will cause it to freeze or not depends on it's content. In my case it freezes Unity :( So you say that using while inside Update is generally ok, given one uses it carefully? I tried using if but it didn't work. I also tried calling a function that changes the tag, yield-waits for a specific amount of time and reverts it back to normal but this works only the 1st time myBoolean becomes true.I'll leave it for the next year as It's getting late for that. Hey Ejlersen,happy 2011!

Ejlersen · Dec 31, 2010 at 07:52 PM 0

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Correct, while-loops does not freeze the program, if used correctly. An infinite loop will freeze your program in all cases. Happy new year :)

RandomCharacters · Sep 04, 2013 at 07:42 AM 0

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so if I use the following, then how does one break out of it??

function $$anonymous$$oving() { while (true) { //some code } yield WaitForSeconds(5.0f); }

Answer 2

Answer by Loius · Dec 31, 2010 at 06:25 PM

Infinite loops freeze Unity, no matter where they are. (Actually they just crash it; a much nicer alternative. thanks devs!)

If you want something to be true while something else is true, you don't use while. Update is its own "while( game playing )" function (of sorts). You use ifs:

if ( ready ) tag = awesome;
else if ( !ready ) tag = notawesome;

Whiles (as explained above) are for conditions that exit eventually -

while ( transform has children ) {
  AFunction( childZero ); 
  RemoveChildZero(); 
}

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schwertfisch · Jan 01, 2011 at 08:07 AM 0

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Thanks a lot Vicenti :) This helps in understanding "while" use. $$anonymous$$y initial approach was the use of if...else but for some reason that did not work and I ended up solving my problem in another way. Thanks again!

POLYGAMe · Mar 23, 2012 at 08:59 AM 0

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Hmm, I have a load of while(true) loops (naughty, I know) in my current project and I haven't had a crash. I'm calling them from start, when I try using any kind of while loop in update it crashes on me... which is understandable as the update function is basically a big while loop!

Bunny83 · Mar 23, 2012 at 10:37 AM 0

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You propable use coroutines which is a totally different story. Unity uses only one thread, so all code runs sequential. If you have any kind of code that get stucks in one place, everything else (in this thread) will be freezed. Coroutines can "break out" of any kind of loop with yield. This keyword will yield the control back to Unity.

Reizla · Jan 29, 2015 at 07:11 AM 0

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Not entirely true..

I agree that infinite loops DO freeze Unity, but Unity also freezes after tries for a loop. I had a program where a while loop checked on a 75% chance and even that made Unity freeze.

Answer 3

Answer by VillainT_ · Nov 27, 2012 at 03:41 PM

You can use (for javascript)

 while (condition) {
 //codes
 yield WaitForSeconds (0);
 }

http://forum.unity3d.com/threads/160337-How-to-use-while-loop-without-crashing-the-game?p=1096760#post1096760

but not use on update function

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