Coroutines what are they | Official Unity Discord | Page 1

karmic basin Dec 22, 2021, 9:49 AM

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test

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Okay good

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So, let's go out of Unity for a moment, and explore what they are and how they're used outside of Unity, in standard C# apps for example.

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What Unity names "coroutines" is more commonly referred as "iterator methods". They're methods that, when ran multiple times, return a different value.

shrewd ledge Dec 22, 2021, 9:52 AM

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what does returning a value mean

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how do they return

karmic basin Dec 22, 2021, 9:53 AM

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I thought you did the C# basics

shrewd ledge Dec 22, 2021, 9:53 AM

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i only know code structure and usage

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so yeah

karmic basin Dec 22, 2021, 9:53 AM

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Returning means passing back a value to the code that executed (called) the method

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Using the return instruction

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void Method1() {
    int number;

    number = Method2();
}

int Method2() {
    return 42;
}

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Take this example

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Method2 returns a number, 42, when called (executed)

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And in Method1, we actually call the Method2.

shrewd ledge Dec 22, 2021, 9:56 AM

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yes

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but

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what does the code do with the 42

karmic basin Dec 22, 2021, 9:57 AM

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So Method2 executes, and returns 42, and in Method1 we intercept that return value and store it into a variable, number

shrewd ledge Dec 22, 2021, 9:57 AM

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oh okay

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but what would happen if there wasnt void method 1
the returned 42 wouldnt do anything?

karmic basin Dec 22, 2021, 9:59 AM

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It would not return anything, as Method2 is never executed

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A method only returns when called

shrewd ledge Dec 22, 2021, 10:00 AM

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so basically, when doing coroutines
the StartCoroutine calls the IEnumerator and gets the value that is returned from it?

karmic basin Dec 22, 2021, 10:01 AM

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That's a bit more complicated.
If you understand what a return value is now, we can go back to coroutines, also named iterators

shrewd ledge Dec 22, 2021, 10:01 AM

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ok

karmic basin Dec 22, 2021, 10:02 AM

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karmic basin What Unity names "coroutines" is more commonly referred as "iterator methods". T...

So, back up here.
A normal method only returns once, otherwise you get an error.
But iterators can yield multiple values.

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Example coming up...

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private IEnumerator GetNumbers()
{
     yield return 1;
     yield return 2;
     yield return 4;
     yield return 8;
}

Here's an iterator, that, when called multiple times, will return a number.
An iterator can be spotted as:

It uses the IEnumerator return type,
It contains at least one yield instruction.

shrewd ledge Dec 22, 2021, 10:08 AM

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so when you call it one time it will return 1
if you call it the second time it will return 2
if you call it the third time it will return 3
does this work like that?

karmic basin Dec 22, 2021, 10:09 AM

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Let's execute it now. Calling GetNumbers() once, execution reaches the first yield instruction, and returns 1. Execution bails out of the iterator, so it can continue later on

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Yeah exactly

shrewd ledge Dec 22, 2021, 10:10 AM

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ok now the 2nd question: what will happen to whats returned

karmic basin Dec 22, 2021, 10:10 AM

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Well, that depends on your code

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Reminder that we're still outside of Unity here

shrewd ledge Dec 22, 2021, 10:10 AM

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ok i think i understand that now

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however in my case i dont want to return anything

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so why do i use this

karmic basin Dec 22, 2021, 10:11 AM

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Hang, on, still not in Unity, and the explanation is not finished

shrewd ledge Dec 22, 2021, 10:11 AM

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ok

karmic basin Dec 22, 2021, 10:14 AM

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Taking the example iterator above, you could do the following

foreach (int number in GetNumbers())
{
    print(number);
}

And that will execute GetNumbers as long as it returns a value, so it will in term print out all the values to whatever console you're using

shrewd ledge Dec 22, 2021, 10:15 AM

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yeah i understand that

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thats like shown in the first example

karmic basin Dec 22, 2021, 10:16 AM

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Okay, so now let's go back to Unity

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Unity uses a loop like the one above to handle coroutines, but you don't see it as it's part of the inner workings of Unity

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So let's take the simplest coroutine possible

private IEnumerator Coroutine()
{
    Debug.Log("before yield");
    yield return new WaitForSeconds(2);
    Debug.Log("after yield");
}

shrewd ledge Dec 22, 2021, 10:19 AM

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nothing is returned

shrewd ledge Dec 22, 2021, 10:20 AM

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karmic basin Taking the example iterator above, you could do the following ```cs foreach (int...

if you were to do something like this, there would be nothing you could return in this example

karmic basin Dec 22, 2021, 10:20 AM

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And now, you start it with StartCoroutine(Coroutine());.
StartCoroutine is a Unity method that will do all the looping work for us.

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So, execution starts

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The first Debug.Log is hit, and it's printed to the console.

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Then, it hits the first yield instruction. And it tells to yield a new WaitForSeconds(2), which is a one-liner to say "create a new WaitForSeconds object, and yield it back"

shrewd ledge Dec 22, 2021, 10:23 AM

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what does yield mean

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as a verb

karmic basin Dec 22, 2021, 10:25 AM

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Means "give way", ie. let other things do whatever they need, and pick back what you were doing later on

shrewd ledge Dec 22, 2021, 10:26 AM

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ohhh ok

karmic basin Dec 22, 2021, 10:27 AM

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So that (the WaitForSeconds) gets picked up by the inner working of Unity. It gets processed in some way (can't explain further, we don't have access to the code), and a Timer is started because we want to wait for two seconds.
Once the timer is elapsed, Unity calls our Coroutine() one more time, and execution picks back up where it left off, right after the first yield instruction. The second Debug.Log call is executed, and printed to the console.
The method finishes, and the coroutine is stopped.

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And that's it. That's literally how they do it

shrewd ledge Dec 22, 2021, 10:30 AM

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i kinda understand it, but still its really complicated for me

karmic basin Dec 22, 2021, 10:31 AM

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Practice will make that simpler to understand

shrewd ledge Dec 22, 2021, 10:31 AM

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however while you were explaining me stuff i got to almost fix my problem using coroutines

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this seems to be working

2021-12-22_11_31_28-gamename_-_Microsoft_Visual_Studio.png

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not entirely but its working quite well

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the only problem is that its very not smooth

karmic basin Dec 22, 2021, 10:34 AM

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I have to go unfortunately, so I'll close the thread and you can repost your question back to the main channel.
I would say the first issue is the integer division you're doing (13/60), that will not behave how you want it to.
You need to do 13f / 60 to forcefully convert one to a float, giving back a decimal number.

#Coroutines what are they