目标C：如何7 - 1 = 3？ [英] Objective C: How does 7 - 1 = 3?

问题描述

NSLog(@"Before: %d",currentArticle);
currentArticle--;
NSLog(@"SUBTRACT %d",currentArticle);

currentArticle是整数。这只是正在我的控制台回荡一次。如果我不运行这个减法，数字currentArticle保持在7。

"currentArticle" is an integer. This is only being echoed once in my console. If I do not run this subtraction, the number "currentArticle" remains at 7.

这是在主线程正在运行，并且仅根据用户交互来运行一次。

This is being run in the main thread, and only run once per user interaction.

我也试过

currentArticle = currentArticle - 1;

使用相同的结果。我是不是疯了服用药丸？

With the same result. Am I taking crazy pills?

谢谢！

编辑：

声明如下：

extern int *currentArticle;

和后来的分配：

currentArticle = 0;

---

我试着重写，因为这：

---

I tried rewriting as this:

int *curArticle; // in my .h file

curArticle = 1;

然后我运行

curArticle--;

和它仍然由两个递减...

and it still decrements by two...

我已经通过code加强并确保没有其他电话打这个变量..感谢您的反馈到目前为止，我会坚持下去劈砍而去。

I have stepped through the code and ensured there are no other calls hitting this variable.. Thanks for the feedback so far, I will keep hacking away at it.

推荐答案

我同意上述意见。我敢打赌一块钱，你的code如下：

I concur with the comments above. I'd bet a dollar that your code looks like:

int *currentArticle = 7; // or something

currentArticle甚至不是一个指向一个int，具体，但它很可能指向一些4字节类型。在' - '和'+'经营者，当通过的指向的类型的大小应用于指针，递减或递增

currentArticle may not even be a pointer to an int, specifically, but it's very likely a pointer to some 4-byte type. The '--' and '++' operators, when applied to pointers, decrement or increment by the size of the type that's pointed to.

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