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

问题描述

self.myVariable = obj; 和 myVariable = obj; 之间有什么区别， code> @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

重要的是注意点语法被编译器转换为一个简单的objc_msgSend调用：也就是说它的下面的行为就像一个消息发送到该变量的访问器。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导致完整的消息发送，意味着调用新功能和与之相关的所有开销。相反，使用简单赋值（myVariable = obj;）不会产生这种开销，但是它只能在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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