virtual function definition

[newbie]

Need a virtual function be redeclared in child class? I thought it's
not necessary, but g++ compiler complains that I didn't declare foo()
in B_Foo. I thought I can optionally do it because AbstractFoo already
does so. am I right?

Thanks

//class.h
class AbstractFoo {
public:
virtual void foo() = 0;
}

class A_Foo : public AbstractFoo{
public:
virtual void foo();
void A_func() { return; }
}

class B_Foo : public AbstractFoo {
public:
void B_func() {return;}
}

//class.cc
void A_Foo::foo() {
// ....
}

void B_Foo::foo(){
//...
}

[Andre Kostur]

newbie <mi******@yahoo.comwrote in news:1182898648.336447.35930
@d30g2000prg.googlegroups.com:

Need a virtual function be redeclared in child class? I thought it's
not necessary, but g++ compiler complains that I didn't declare foo()
in B_Foo. I thought I can optionally do it because AbstractFoo already
does so. am I right?

Virtuals must be redeclared in a child class? Not necessarily. However,
your foo() function is a _pure_ virtual function, so it must be
redeclared.

Thanks

//class.h
class AbstractFoo {
public:
virtual void foo() = 0;
}

class A_Foo : public AbstractFoo{
public:
virtual void foo();
void A_func() { return; }
}

OK, A_Foo declares a foo() method, so A_Foo will be instantiatable (you
can create a variable of this type).

class B_Foo : public AbstractFoo {
public:
void B_func() {return;}
}

B_Foo does not declare a foo() method, so B_Foo will not be
instantiatable. Hopefully sometime in the future B_Foo will have a child
class which will declare a foo().

//class.cc
void A_Foo::foo() {
// ....
}

void B_Foo::foo(){
//...
}

The compiler let you do this? B_Foo::foo() doesn't exist!