Summary of complex and fragmented knowledge points (updated from time to time)

 

1. Static nsstring * const

Static:

A. Local static variables: initialization once. Initialization is not performed for the next call.

B. External static variables/functions: used for scope restrictions. They are only used in this file.

C. static data member/member function (C ++): For a class rather than a specific object, for example, counting in a class

Const:

A. Define a const constant: const double Pi = 3.1415

B. Protect the modified items to prevent accidental modification: const int I {I = 1; // an error is reported when the modification is performed}

C. If the const is on the left side of *, it is used to modify the variable pointed to by the pointer, indicating that the pointer is a constant. If the const is on the right side of *, it is used to modify the pointer itself, indicating that the pointer is a constant.

Static nsstring * const:

The pointer content and pointer pointing cannot be changed.

Summary of complex and fragmented knowledge points (updated from time to time)