Objective-C使用动态绑定，但是如何? [英] Objective-C uses dynamic binding, but how?

问题描述

我知道Objective-C对所有方法调用都使用动态绑定.如何实施?在编译之前，objective-c会变成C代码"并且仅对所有内容使用(void *)指针吗?

I know that Objective-C uses dynamic binding for all method calls. How is this implemented? Does objective-c "turn into C code" before compilation and just use (void*) pointers for everything?

推荐答案

从概念上讲，正在发生的事情是存在一个调度程序库(通常称为Objective C运行时)，并且编译器将进行如下转换: /p>

Conceptually, what is going on is that there is a dispatcher library (commonly referred to as the Objective C runtime), and the compiler converts something like this:

[myObject myMethodWithArg:a andArg:b ];

进入

//Not exactly correct, but close enough for this
objc_msgSend(myObject, "myMethodWithArg:andArg:", a, b);

然后，运行时处理所有绑定和分派，找到合适的函数，并使用这些args对其进行调用.简而言之，您可以认为它类似于哈希查找.当然，要比实际要复杂得多.

And then the runtime deals with all the binding and dispatch, finds an appropriate function, and calls it with those args. Simplistically you can think of it sort of like a hash lookup; of course it is much more complicated that then in reality.

还有更多与方法签名等问题相关的问题(C不对类型进行编码，因此运行时需要对其进行处理).

There are a lot more issues related to things like method signatures (C does not encode types so the runtime needs to deal with it).

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