Implementation of Objective-c method

The Objective-c method is described by two data types: One is the selection sub (SEL), which describes the name of the method, and the other is the implementation (IMP), which describes the code that is actually executed when the method is called (they are basically pointers to the C function).

Like the SEL structure, IMP can be obtained through the runtime and can also be passed (as a parameter) to functions and methods.

In most cases, you only use the selector. You only use the IMP structure when accessing some of the OBJECTIVE-C runtime advanced features.

You can think of it this way: SEL is an abstract representation of a objective-c method, and IMP is a concrete implementation.

Implementation of Objective-c method