How to prevent Coroutines from freezing Unity?

Unity Engine
1

Whenever I use Coroutines there is always a risk of it completely freezing my game upon pressing play.

For example I’m making a little game where both player and enemies have Coroutines to shoot with delay, rather than constantly. Everything works fine but when I add while() to something the game freezes upon starting it.

Player Coroutine…
Starts in the PlayerScript when GetMouseButtonDown(0) and ends when GetMouseButtonUp(0)

IEnumerator FireContinuously()
    {
        while (true)
        {
            GameObject playerProjectile = Instantiate(projectile, transform.position, Quaternion.identity) as GameObject;
            playerProjectile.GetComponent<Rigidbody2D>().velocity = new Vector2(direction.x * projectileSpeed, direction.y * projectileSpeed);
            yield return new WaitForSeconds(firingSpeed);
        }
    }

Enemy Coroutine…
Starts in the EnemyGun Start() and runs constantly

IEnumerator EnemyShootGun()
    {
        while (true)
        {
            yield return new WaitForSeconds(UnityEngine.Random.Range(firingSpeed, firingSpeed + firingSpeed));
            GameObject enemyProjectile = Instantiate(projectile, transform.position, Quaternion.identity) as GameObject;
            enemyProjectile.GetComponent<Rigidbody2D>().velocity = new Vector2(direction.x * projectileSpeed, direction.y * projectileSpeed);
        }
    }

Code causing my game to freeze…
Public method in the EnemyScript Start() that moves the enemy to certain waypoints

public void EnterArena()
    {
        int targetPosition = 0;
        transform.position = wayPoints[targetPosition].transform.position;

        while(targetPosition < wayPoints.Count)
        {
            Debug.Log("testing");
        }
    }

I would really appreciate if someone knew what is going on as my other games were also plagued by Coroutines freezing after implementing while() somewhere.

Additional info:
Both player and enemies are made of parent object that has two children

Parent - has script (EnemyScript / PlayerScript) controlling movement and behavior
Child(hull) - just sprite
Child(gun) - gun sprite with code to control its rotation and shooting (EnemyGun / PlayerGun)

2

Don’t use while loops.
As long as the while loop is true it will execute the code within and stop executing other code.
Coroutines are not asynchronous. They run in steps on the main thread.

You rather want to change your code where it involves calling the “fire” method multiple times.

Something like

for (var i = 0; i < N; i++)
{
Fire();
yield return new WaitForSeconds(interval);
}

that’ll call the fire method multiple times for N amount of times with intervals in between.

1 Like
3

You have got to yield return null; in there. Until you exit the loop, everything is frozen.

It actually has nothing to do with coroutines and has nothing to do with how you loop. It’s the simple failure to return control to Unity so it can update the game to the next frame.

4 Likes
4

To add on to Kurt’s answer and be more specific about what’s causing the infinite loop here:
targetPosition is initialized as 0. The Count of the list will always be at least 1. Nothing in the while loop changes the value of either targetPosition or the list’s Count, so targetPosition < wayPoints.Count will always evaluate to true, which means there is no possible way to break the loop.

1 Like
5

Well, sure coroutine while-loops almost always want a yield, but the code with that loop isn’t a coroutine. I’m not sure what it’s even for, or if the OP wanted it to be a coroutine.

A decent pair of rules is: 1) in a coroutine, double-check that every loop has a yield – any kind. 2) a non-coroutine doesn’t need a loop – it’s being called from Update, which is already a loop.

1 Like
6

Oh yeah, good spot, my bad.

Perhaps OP wanted to make sure nothing else moved forward until all the waypoints had been hit, like an intro to the arena or something (just speculating)…