How to wait in Unity c# function?

Question

I have to make a code where the cube disappears in a couple of seconds after the player touches it. But I have no idea how to make it because StartCoroutine(name()); works only in IEnumerator name(){} like this:

void Start()
{
    StartCoroutine(waiter());
}

IEnumerator waiter()
{    
    //Wait for 4 seconds
    yield return new WaitForSeconds(4);  
}

but I need to wait in private void OnCollisionEnter(Collision collision) {} function. I can't do something like this:

void start()
    {
        StartCoroutine(Text());
    }

    IEnumerator Text() 
    {
        private void OnCollisionEnter(Collision collision)
        {
            yield return new WaitForSeconds(3);
            StartCoroutine(Text());
            rd = GetComponent<Renderer>();
            rd.enabled = false;
        }
        

    }

How to make a cooldown in OnCollisionEnter function?

the trivial way to do things like this in Unity is simply the Invoke command. It couldn't be easier. — Fattie
– Fattie, Commented Dec 7, 2020 at 18:34
@Fattie to me Invoke has its good side and also a bad one: It is not cancelable. The Coroutine can still be stopped if e.g. the component is disabled in the meantime (let's e.g. say you open a Pause menu). The Invoke will be invoked after the time passed no matter what ;) — derHugo
– derHugo, Commented Dec 8, 2020 at 11:09
You know, there is actually a cancel-invoke believe or not! docs.unity3d.com/ScriptReference/… My point is just that for beginners, for trivial timers like this, you can just use "Invoke" - which is I'd say the very reason Unity tossed it in, make it easy for hobbyists ... — Fattie
– Fattie, Commented Dec 8, 2020 at 11:58

Immersive · Accepted Answer · 2020-12-07 09:49:43Z

1

void Start() { }

private void OnCollisionEnter(Collision collision) {
    StartCoroutine(Text());
}

IEnumerator Text() 
{
    yield return new WaitForSeconds(3);
    rd = GetComponent<Renderer>();
    rd.enabled = false;
}

answered Dec 7, 2020 at 9:49

Immersive

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Comments

derHugo · Accepted Answer · 2020-12-07 14:03:20Z

1

Your nested methods make no sense.

Why not simply make OnCollisionEnter a Coroutine itself:

// Best you already reference this via the Inspector in Unity
[SerializeField] private Renderer _renderer;

private void Awake ()
{
    // Alternatively get it ONCE on runtime
    if(!_renderer) _renderer = GetComponent<Renderer>();
}

private IEnumerator OnCollisionEnter(Collision collision)
{
    yield return new WaitForSeconds(3);
   
    _renderer.enabled = false;
}

answered Dec 7, 2020 at 14:03

derHugo

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4 Comments

Charleh Over a year ago

Isn't OnCollisionEnter auto-wired by Unity though? I thought it required a specific signature as it's called by rigid body in response to collision events - does it automatically get executed as a coroutine if you build the method signature to look like one (might be useful info for someone else)?

derHugo Over a year ago

Yes, but if you make it IEnumerator it is automatically started as a Coroutine by Unity ;) Works with most event based messages except some exceptions like e.g. Awake, Update, OnDestroy .. but works with e.g. Start, OnTriggerEnter, OnCollisionEnter, OnTriggerExit, `OnCollisionExit, ...

Charleh Over a year ago

That's useful info to know, I didn't find that in the docs

derHugo Over a year ago

@Charleh yep it's pretty hidden ^^ see e.g. at the bottom of OnCollisionEnter -> OnCollisionEnter can be a co-routine, simply use the yield statement in the function. .. a bit confusing tbh it would be way better to understand if they would simply say ...simply let it return IEnumerator because that is what is ment actually ;)

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