自变量和变量差异 [英] self.variable and variable difference

问题描述

self.myVariable = obj; 和 myVariable = obj; 有什么区别，当我使用 @propery/@synthesize 创建`myVariable?

What is the difference between self.myVariable = obj; and myVariable = obj;, when I use @propery/@synthesize to create `myVariable?

推荐答案

需要注意的是，编译器将 dot-syntax 转换为一个简单的 objc_msgSend 调用:也就是说，它的作用与发送到的消息完全一样该变量的访问器.因此，以下所有三个都是等效的:

It's important to note that dot-syntax is converted to a simple objc_msgSend call by the compiler: that is to say that underneath it acts exactly like a message send to the accessor for that variable. As such, all three of the following are equivalent:

self.myVariable = obj;

[self setMyVariable:obj];

objc_msgSend(self, @selector(setMyVariable:), obj);

当然，这意味着使用点语法实际上会导致完整的消息发送，这意味着调用一个新函数以及与之相关的所有开销.相比之下，使用简单赋值 (myVariable = obj;) 不会产生任何此类开销，但当然只能在相关类的实例方法中使用.

Of course, this means that using dot-syntax actually results in a full message send, meaning calling a new function and all the overhead that is associated with it. In contrast, using simple assignment (myVariable = obj;) incurs none of this overhead, but of course it can only be used within the instance methods of the class in question.

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