Virtual methods

6 Virtual methods

Virtual methods work the same way in the case of multiple inheritance as in the case of single inheritance. Let us examine the example in listing 5.

Listing 5:

virtualmethod

1class A
2{
3  public:
4    virtual void m1(void) {}
5    void concreteA(void) { m1(); }
6};
7
8class B
9{
10  public:
11    virtual void m1(void) {}
12    void concreteB(void) { m1(); }
13};
14
15class C : public A, public B
16{
17  public:
18    virtual void m1(void) { A::m1(); B::m1(); }
19};
20
21void test(void)
22{
23  C myC;
24  A *pA = &myC;
25  B *pB = &myC;
26
27  pA−>m1();
28  pA−>concreteA();
29  pB−>m1();
30  pB−>concreteB();
31}

In this case, both line 27 and line 29 invoke C::m1, which in return calls the m1 of both superclasses.

Note that line 28 ends up calling C::m1(), and line 30 ends up calling C::m1() as well.

This is because the invocation of line 5 is determined at run time.

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