Class member pointer classname: * Member, (classname: * PF )()

Review:

Definition of common function pointers1 Int(*PFI )()

Question:
Suppose there are the following classes: 1 Class Screen
2 {
3 Public :
4 Int Height (){ Return _ Height ;}
5 Int Width (){ Return _ Width ;}
6 // .
7 }

Now assign a value1 PFI= &Screen: height;
2 //Illegal value assignment, type violation

Because the pointer to a member function contains three aspects: 1) parameter table (number, type) 2) return type 3) class type
The normal pointer to a function contains only two aspects.

correct pointer definition to a member function: 1 int (screen :: * PMF) ();
2 PMF = & screen: height;
3
4

To avoid complex pointer types, use typedef1 TypedefInt(Screen*Ptr_type )();
2 Ptr_type PMF= &Screen: height;

Note:Classname ::*Syntax

Usage of pointers to class members: 1 Int (Screen :: * PMF )() =   & Screen: height;
2 Screen myscreen, * Bufscreen;
3
4 // Directly call member functions
5 If (Myscreen. Height () = Bufscreen -> Height ())
6 //
7
8 // Equivalent call through the member function pointer
9 If (Myscreen. * PMF )() = (Bufscreen -> * PMF )())
10 //

In the same way, point to the data member pointer:1 IntScreen ::*Ps_screen= &_ Height

Conclusion: Compared with common pointersClassname ::*

Static member pointer:
We know that static class members belong to global objects and functions of the class, and their pointers are normal pointers (remember that static member functions do not use this pointer)

1 Class Classname
2 {
3 Public :
4 Static   Void Rai ( Double Incr );
5 Static   Double Interest (){};
6 //
7 Private :
8 Static   Double _ Interestrate;
9 String _ Owner;
10 }
11
12 // OK
13 Double   * PD =   & Classname: _ interestrate;
14 // Error
15 Double Classname :: * PD =   & Classname: _ interestrate;
16
17 // OK
18 Double ( * Pfunc )() =   & Classname: interest;