How to pass pointer of class member function __ Programming Technology

Demand:

In Class A, there is a set of functions with the same specification;

Class B has a pointer to member F in a member function, initializes the member F when constructing a B object, and then calls the function of the function pointer in the DO function.

What needs to be done to achieve this goal.

Class A Void F1 (); Void F2 (); Void F3 ();

Class B B (f) Do () { F (); } F A * PA;

One feature of C + + is needed here: a member function pointer. This feature is generally rarely used, so the feeling is more obscure, using the following points:

1. Use a typedef to define the type of a member function pointer:

typedef void (A::* FunC) ();

This defines the Func as a null return value type in Class A and a null function pointer for the argument list.

2. Statement in B

FunC F;//To declare F as a pointer to a member function in a.

3. Declare the constructor of B

B (* A, Func f) {PA = A; f = f;}

4. Do in the following call:

(pa->*f) ();

5. Externally constructs a, B objects, and makes method calls.

A A;

B B1 (&a, &A::F1);

B1.  Do (); This will call the F1.

B B2 (&a, &A::F2);

B2.  Do (); This will call the F2.

Special Note:

C + + member functions implicitly have a this argument, that is, to invoke the Class object's member function, you must first have the object of the class, and therefore, in B's constructor to pass a object address in.