Objective C message dispatch mechanism

problem ：

I am just staring to play around with Objective C (writing toy iPhone apps) and I am curious about the underlying mechanism used to dispatch messages. I just want to play Objective C（ Writing toys iPhone Applications ）, I'm curious about the underlying mechanism for sending messages .I have a good understanding of how virtual functions in C++ are generally implemented and what the costs are relative to a static or non-virtual method call, but I don't have any background with Obj-C to know how messages are sent. I know very well C++ How to implement virtual functions in , And the cost relative to static or non virtual method calls , But I don't have any Obj-C Background to understand how messages are sent .Browsing around I found this loose benchmark and it mentions IMP cached messages being faster than virtual function calls, which are in turn faster than a standard message send. When browsing, I found This Loose benchmarks , It refers to IMP Cached messages are faster than virtual function calls , Virtual function calls are faster than standard messages .

I am not trying to optimize anything, just get deeper understanding of how exactly the messages get dispatched. I'm not trying to optimize anything , Just learn more about how messages are sent .

• How are Obj-C messages dispatched?Obj-C How messages are sent ？
• How do Instance Method Pointers get cached and can you (in general) tell by reading the code if a message will get cached? How instance method pointers are cached , Can you （ Usually ） Read the code to determine whether a message will be cached ？
• Are class methods essentially the same as a C function (or static class method in C++), or is there something more to them? Class methods are essentially the same as C function （ or C++ Static class methods in ） identical , Or do they have more things ？

I know some of these questions may be 'implementation dependent' but there is only one implementation that really counts. I know some of these problems may “ Depend on the realization ”, But only one implementation is really important .

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Solution ：

Reference resources ： https://stackoom.com/en/question/47Ua