Question

我正在通过Objective-C进行scanf倒计时，因此程序将从您输入的数字开始倒计时。但是，代码中存在一个恼人的语义错误：格式字符串不使用数据参数。程序也没有倒计时，只要输入一个数字，它就会将输出显示为零。

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{

    @autoreleasepool {

        int x,number;

        NSLog(@"please enter a number:");
        scanf("i", &number);
        for (x = number;  x>=0; x--)
            NSLog(@"%i",x);
    }
    return 0;
}

Answer 1

你没有说你遇到了什么麻烦，或者你试图解决它的问题，所以人们很难帮助你。

但是对于初学者来说，你发布的代码片段（a）永远不会给y一个值;（b）循环永远不会在你设置count = 1然后测试{{1}时执行} - 将立即失败而不进入循环。

对于（a）我只能猜到你期望count == 3来自哪里，因为（b）你可能意味着y - 即循环3次？

评论后的附录

好的，让我们重新编写你的代码并添加一些注释。 count <= 3循环可以重写为for循环，在您的情况下，它看起来像：

while

进行上述更改并恢复为count = 1; // initialize while (count == 3) // Test, will fail immediately, did you mean count <= 3? { NSLog(@"enter a number"); scanf("%i", &x); // At this point you have set x to a value // however y has no value - as it is a local variable it has some random value // the next line calculates `y%x`, and without a value for y this calculation // is meaningless. Did you mean to read in both x and y? E.g. scanf("%i%i", &x, &y)? // Note you should also check the return value from scanf, it is the number of items // successfully converted - while you may "enter a number" your user might type // "sixteen", which is a number to them but scanf won't parse it with %i! if (y%x == 0) NSLog(@"%i is evenly divisible by %i", y, x); else NSLog(@"%i is NOT evenly divisible by %i", y, x); count++; // increment }会产生：

for

HTH

Answer 2

你的scanf语法错误应该是

scanf("%i",&number) //for integer

与scanf功能一起使用

2 个答案: