Which to use Coroutine or Update to slow down animation

Question

I want to do

1. gradually stop car animation as it collildes with another car
2. gradually speed up car animation as it exit the collider

And I have two ways to acheive this thing(means to run my logic in).

1. Update
2. Co-routine

for coroutine I used this

IEnumerator IncreaseSpeedGradually1(AnimationControlSpeed lastGOHitScript)
{
    //stop if decrease speed in progress
    StopCoroutine("DecreaseSpeedGradually");
    float decrementValue = ((lastHitVehicleSpeed / 2) * 2);
    while (lastGOHitScript.Speed <= lastHitVehicleSpeed)
    {
        lastGOHitScript.Speed += decrementValue * Time.deltaTime;
        yield return 0;
    }
    //setting speed to the last speed
    lastGOHitScript.Speed = lastGOHitScript.iniSpeeed;
}

While for update I just make this criteria:

if (carAnimState == carAnimationState.starting)
{
    carAnimState = carAnimationState.running;
}

if (carAnimState == carAnimationState.stoping)
{
    carAnimState = carAnimationState.running;
}

These two ways I know but i want to ask that which is right way to do this job? to slow down animation speed and hence get my objective? I guess corroutine later can be problematic in my game and what are the performance concerns?

Answer 1

Not perfectly clear what your goal exactly is. What you describe is clear, but the two code snippets you posted do completely different things. BUT, basically, for something this small I would use Update() as it's easier to debug if something blows up and there's nothing -theoretically- in your code that wishes "threading" / "side tasking" (which coroutines are for, basically: do something -most probably a side task- async).

As a side note, the code in your Update() can be optimized a little so it will look something like this:

if (carAnimState == carAnimationState.starting) {
    carAnimState = carAnimationState.running;
} else if (carAnimState == carAnimationState.stoping) {
    carAnimState = carAnimationState.running;
} //this way the 2nd "if" won't be unnecessarily evaluated when animstate was .starting

I'd also add a method instead and call that from Update(). The pre-compiler will inline it most probably (cannot be forced in Unity) and your code is more readable.