Two rules to be followed by the C ++ member pointer

 

Rule 1: * it needs to be combined with indirectly referenced objects. Because there is no address in the class, the member pointer only indicates a certain offset in the object.

Rule 2: when getting the member function address (offset address), the symbol & is necessary, which is different from the usage of the non-member function pointer.

 

Case 1:

 

//: PointerToMemberData. cpp

# Include <iostream>

Using namespace std;

 

Class Data

{

Public:

Int a, B, c;

Void print () const

{

Cout <"a =" <a <", B =" <B

<", C =" <c <endl;

}

};

 

Int main ()

{

Data d, * dp = & d;

Int Data: * pmInt = & Data:;

Dp-> * pmInt = 47; // Rule 1

PmInt = & Data: B;

D. * pmInt = 48;

PmInt = & Data: c;

Dp-> * pmInt = 49; // Rule 1

Dp-> print ();

}

Case 2: www.2cto.com

 

//: PointerToMemberFunction. cpp

# Include <iostream>

Using namespace std;

 

Class Widget

{

Public:

Void f (int) const {cout <"Widget: f () \ n ";}

Void g (int) const {cout <"Widget: g () \ n ";}

Void h (int) const {cout <"Widget: h () \ n ";}

Void I (int) const {cout <"Widget: I () \ n ";}

};

 

Int main ()

{

Widget w;

Widget * wp = & w;

Void (Widget: * pmem) (int) const = & Widget: h; // Rule 2

(W. * pmem) (1); // Rule 1

(Wp-> * pmem) (2); // Rule 1

}

Case 3:

 

//: PointerToMemberFunction2.cpp

# Include <iostream>

Using namespace std;

 

Class Widget

{

Void f (int) const {cout <"Widget: f () \ n ";}

Void g (int) const {cout <"Widget: g () \ n ";}

Void h (int) const {cout <"Widget: h () \ n ";}

Void I (int) const {cout <"Widget: I () \ n ";}

Enum {cnt = 4 };

Void (Widget: * fptr [cnt]) (int) const;

Public:

Widget ()

{

Fptr [0] = & Widget: f; // Rule 2

Fptr [1] = & Widget: g;

Fptr [2] = & Widget: h;

Fptr [3] = & Widget: I;

}

Void select (int I, int j)

{

If (I <0 | I> = cnt)

Return;

(This-> * fptr [I]) (j); // rule 1, this is required

}

Int count () {return cnt ;}

};

 

Int main ()

{

Widget w;

For (int I = 0; I <w. count (); I ++)

W. select (I, 47 );

}

 

Author: yucan1001