Non-static member variables or non-static member functions in the class called in the callback function

The callback function calls non-static member variables or non-static member functions in the class.

[Question] How do I encapsulate callback functions in a class?
A. the callback function can only be global or static;
B. Global functions will damage the class encapsulation, so they will not be used;
C. Static functions can only be static members of the callback class. They cannot be non-static members of the callback class.
 
1. How to make non-static members of the callback class of the static function.
A. Declare a static function a () and pass the class instance object pointer as a parameter. For example:

 
ClassA (){Static VoidA (*);//Static FunctionsVoidB ();//Non-static functions}VoidA: A (*Pthis) {pthis-> B ();//Call non-static functions in static functions}
 

B. Access non-static members in the callback function
Since the callback function is often fixed and does not accept the * pthis Parameter
For example, callback mytimerproc (hwnd, uint umsg, uint idevent, DWORD dwtime );

[Solution 1]: This solution has problems when there are multiple class instance objects. The reason is that the pthis pointer can only point to one object.

 Class  A (){  Static   Void A (); //  Static callback function        Void B (); //  Non-static functions        Static A * pthis; // Static object pointer  }  //  The constructor assigns this pointer to pthis so that the callback function can access this object through the pthis pointer. A * A: pthis = NULL; A: A () {pthis = This  ;}  Void  A: (){  If (Pthis = Null)  Return  ; Pthis -> B (); // Call non-static functions in the callback function }

[Solution 2]: This solution solves the problem of solution 1 when multiple class instance objects exist. Store all object addresses in the ing table, and each object saves its own ID number.

Typedef cmap <uint, uint, A *, A *> Camap;  Class  A (){  Static   Void A (); //  Static callback function        Void B (); //  Non-static functions        Int M_id; // ID of this object in the list        Static   Int M_sid; //  Static current Object ID. (if necessary, assign m_id to m_sid to call this object function)        Static Camap m_map; //  Static object ing table  } Camap A: m_map;  Int A: m_sid = 0  ;  //  The constructor assigns this pointer to pthis so that the callback function can access this object through the pthis pointer. A: (){  If  (M_map.isempty () {m_id = 1  ;}  Else  {M_id = M_map.getcount () + 1  ;} M_map.setat (m_id,  This  );}  Void  A: (){  If (M_map.isempty ())  Return  ; * Pthis = NULL;  If  (M_map.lookup (m_sid, pthis) {pthis -> B (); //  Call non-static functions in the callback function  };} 

 

[Thank you for your reference]
1. The callback function calls non-static member variables or non-static member functions in the class.