you can easily add methods and attributes with Category through Objective-C Runtime,.
his implementation principle is the object structure, objc_class contains the methodLists, is a secondary pointer, a pointer to the pointer.
struct objc_method_list **methodLists OBJC2_UNAVAILABLE;//
methodLists represents the list of methods, which can be dynamically modified to implement Category.
Resources: https://www.jianshu.com/p/c0b.
is still a little confused, how to understand better
< H2 > specifically, where did you deal with the addition of the method < / H2 >