c - 这个变量的值是如何增加的？ - 代码 objective-c

Question

我目前正在从一本书的教程中学习 C，我正在遵循此代码。

我不明白的是变量 numberOfBottles 是如何在这一行从 1 开始并以 4 结束的。感谢大家的帮助，我对 Objective C 还是个新手

printf("Put a bottle in the recycling, %d empty bottles in the bin.\n", numberOfBottles);


void singSongFor(int numberOfBottles)
{
    if (numberOfBottles == 0) {
        printf("There are simply no more bottles of beer on the wall.\n\n");
    } else {

        printf("%d bottles of beer on the wall. %d bottles of beer.\n",     numberOfBottles, numberOfBottles);
        int oneFewer = numberOfBottles - 1;

        printf("Take one down, pass it around, %d bottles of beer on the wall.\n\n", oneFewer);
        singSongFor(oneFewer); //This function calls itself!

        // Print a mesasge just before the function ends

        printf("Put a bottle in the recycling, %d empty bottles in the bin.\n", numberOfBottles);
    }
}

int main(int argc, const char * argv[])
{
    // We could sing 99 verses, ut 4 is easier to think about
    singSongFor(4);
    return 0;
}

Answer 1

设置断点并尝试理解此代码段的执行，您将了解它是如何工作的。

当我尝试这段代码时，它的执行方式如下:

4 bottles of beer on the wall. 4 bottles of beer.
Take one down, pass it around, 3 bottles of beer on the wall.

3 bottles of beer on the wall. 3 bottles of beer.
Take one down, pass it around, 2 bottles of beer on the wall.

2 bottles of beer on the wall. 2 bottles of beer.
Take one down, pass it around, 1 bottles of beer on the wall.

1 bottles of beer on the wall. 1 bottles of beer.
Take one down, pass it around, 0 bottles of beer on the wall.

There are simply no more bottles of beer on the wall.

Put a bottle in the recycling, 1 empty bottles in the bin.
Put a bottle in the recycling, 2 empty bottles in the bin.
Put a bottle in the recycling, 3 empty bottles in the bin.
Put a bottle in the recycling, 4 empty bottles in the bin.