c - 如何在无限循环中仅运行一个函数一次？

Question

我正在用 C 语言编写一个游戏引擎，它可以在多个旧平台上运行，例如 Sega Saturn 和 PS1。不过，我遇到了一个小问题。游戏有一个主循环，所有其他函数都从该循环中调用。这意味着在不涉及状态的情况下很难只调用一次函数。所以，我需要知道最好的方法。我将展示一个关于如何设置的简短示例:

mainloop() //This function repeats forever
{
    myFunc1(); //Therefore, this function also repeats forever.
}

myFunc1() //Subsequent, gameplay related function
{
    if(myThing == 9){  //This thing is gonna equal 9 for quite a while, so that means the fucntion below will also be called like a bunch. But we don't want it to!
        runFuncOnce(); //Run this function only one time
    }
}

runFuncOnce() //I only want this function to do stuff one time until the next time it gets called!
{
    //Some examples of things you'd only want to do one time:
    PlayASound(MySound);
    ResetAnimation(MyAnimation); //Set an animation back to its first frame
    myVariable = 5; //Set this variable to whatever, but only once!
    printf("Hey, you did a thing. Good job! If you're lucky you won't see this text like 8 billion times in a row")
}

当然，您不想在同一个函数中执行这些操作，但您明白了。有一些愚蠢的方法可以做到这一点，但我正在尝试以最干净、最快的方式做到这一点。我不想谈论我的做法，因为人们很可能会关注我之前尝试过的方式，并尝试解决这个问题。给我新鲜的想法!相信我，我以前的做法既愚蠢又缓慢。这就是我来这里的原因!

Answer 1

您可以使用静态变量。

myFunc1() //Subsequent, gameplay related function
{
    static bool runOnlyOnce = false;

    if(myThing == 9) {  //This thing is gonna equal 9 for quite a while, so that means the function below will also be called like a bunch. But we don't want it to!
        if (runOnlyOnce == false) {
            runFuncOnce(); //Run this function only one time
            runOnlyOnce = true;
        }
    }
}

静态变量值在函数调用之间保持不变。因此，当下次调用 myFunc1() 时，它会找到 runOnlyOnce 变量 true 的值，并且不会调用 runFunOnce()再次。