Re: Does object have function?

From:
"Daniel T." <daniel_t@earthlink.net>
Newsgroups:
comp.lang.c++
Date:
Fri, 29 Oct 2010 07:46:45 -0400
Message-ID:
<daniel_t-EA84A5.07464429102010@70-3-168-216.pools.spcsdns.net>
In article
<2dbb59cb-2dde-44a0-a459-e6ebcd5f3cfd@g13g2000yqj.googlegroups.com>,
 Joshua Maurice <joshuamaurice@gmail.com> wrote:

On Oct 28, 6:02?pm, "Daniel T." <danie...@earthlink.net> wrote:

This would work:

class Base {
public:
? ?virtual ~Base() {}

};

class Fooer {
public:
? ?virtual void foo() = 0;

};

class DerivedOne : public Base, public Fooer {
public:
? ?void foo() { cout << "DerivedOne::foo()\n"; }

};

class DerivedTwo : public Base, public Fooer {
public:
? ?void foo() { cout << "DerivedTwo::foo()\n"; }

};

class DerivedThree: public Base {

};

int main() {
? ?Base* bps[3];
? ?bps[0] = new DerivedOne();
? ?bps[1] = new DerivedTwo();
? ?bps[2] = new DerivedThree();

? ?for ( int i = 0; i < 3; ++i ) {
? ? ? Fooer* thisOne = dynamic_cast<Fooer*>( bps[i] );
? ? ? if ( thisOne )
? ? ? ? ?thisOne->foo();
? ?}

}


With this multiple inheritance design, I would guess that you probably
want to virtually inherit from Fooer as well (not done in the above
code).


Virtual inheritance would only be necessary if Fooer had
member-variables. Inheriting interfaces (classes with only pure virtual
functions and no member-variables,) does not require virtual inheritance.

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