一段时间后结束协程函数内循环的最佳方法是什么？

Question

这是我的第一个问题，我猜一切都很清楚-

协程 (UnityC#) 中的循环行为不正确，或者我做错了什么！检查代码 cmets...

bool loop=true;
bool once=false;   

IEnumerator Fun()
{
    while (loop)
    {
        //those 3 lines must be repeated for the whole 2.5 seconds,am I right! but it only run once so why?
        carRb.drag += .005f;
        Debug.Log("Loop1:"+loop);
        if (!once)          //last rep. line
        { 
            once = true;
            yield return new WaitForSeconds(2.5f); 
            loop = false;
        }
        yield return new WaitForEndOfFrame();
    }
    yield return new WaitForSeconds(2f); //will run this line after 2.5s        
    Debug.Log("Loop2: "+loop);      //will run this line and whats below after (2.5+2s) 
    carRb.drag = 25f;
    carController.canControl = false;
    Destroyed = true; 
}

Answer 1

once值为false，进入if条件后等待2.5s结束循环。

bool loop=true;
bool once=false;

IEnumerator Fun()
{
    float time=0;
    while (loop)
    {
        //those 3 lines must be repeated for the whole 2.5 seconds,am I right! but it only run once so why?
        carRb.drag += .005f;
        Debug.Log("Loop1:"+loop);
        yield return null;  // wait each update call
        time+=Time.deltaTime;
        if (time>2.5f)          //last rep. line
        {
            once = true;
            loop = false;
        }
    }
    yield return new WaitForSeconds(2f); //will run this line after 2.5s
    Debug.Log("Loop2: "+loop);      //will run this line and whats below after (2.5+2s)
    carRb.drag = 25f;
    carController.canControl = false;
    Destroyed = true;
}

Answer 2

最清晰的方式解释这里的误解是：

1. WaitForSeconds 不能在单独的盒子或类似的东西中工作 所以

2. 它会阻止整个代码继续运行，直到时间结束，这意味着即使我们在关闭循环之前等待（设置 loop=false），我们仍将处于第一次迭代中。 结束循环的最好方法是使用数值变量，每帧增加它并检查它是否达到我们想要的时间然后中断

感谢@user3315036 和@Absinthe

代码如下：

IEnumerator Fun(){
    float time=0;

    while(time<2.5f){
        carRb.drag += .005f;
        Debug.Log("Loop1");
        time+=Time.deltaTime;       
        yield return null;

    }
    yield return new WaitForSeconds(2f); //will run this line after 2.5s        
    Debug.Log("2: ");      //will run this line and whats below after (2.5+2s) 
    carRb.drag = 25f;
    carController.canControl = false;
    Destroyed = true; 

}