局部变量设置为nil? (目标C) [英] Local variables set to nil? (Objective-C)

问题描述

我正在阅读有关Objective-C的书，作者说，如果未给局部变量赋值，它们将被设置为nil，而静态变量将被设置为零.因此，我设置了int a并没有为其分配值.然后NSLog(@"%i", a)显示它，而a显示为零.我对此有些困惑，我想知道是否有人可以为我澄清一下?

I'm reading a book on Objective-C and the author said that if local variables aren't assigned a value they will be set to nil, but static variables will be set to zero. So, I set up int a and didn't assign it a value. Then NSLog(@"%i", a) to display it and a was displayed as zero. I was a little confused on that and I was wondering if someone could clarify it for me?

推荐答案

在启用ARC的情况下，无论在何处创建对象，Objective-C对象指针变量都将设置为nil.

With ARC enabled, your Objective-C object pointer variables will be set to nil regardless of where you create them.

没有ARC，并且对于内置C类型，您的变量将不会初始化.

Without ARC, and for built in C types, your variables will not be initialized.

分配对象时，Objective-C对象的实例变量始终设置为0(或nil).

Instance variables of Objective-C objects are always set to 0 (or nil) when you allocate an object.

静态设置为0.

尽管如此，我已经习惯于始终为变量提供默认值.这是一个好习惯.

I've gotten in the habit of always giving a default value to variables, though. It's been a good habit to have.

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