creating a pointer to a base class

[john smith]

Hi, I'm trying to do something like this:

class A {
public:
virtual void f() {
// do something
}
};
class B : public A {
// some methods here
};

class C {
public:
C(A* a)
{
a_ = new WHAT?!?! // could be either A or B!!
}
A* a_;
};

In general, there could be more classes derived from A or B.... Assuming
there are copy constructors and assignment operator defined for A and B.
How can I initalize a_? do I have to resort to RTTI if-else ladders!?
There is got to be a better way!

thanks

Smith

 

[Karl Heinz Buchegger]

Maybe You should write the "clone function for every class (A and B). In
class A
A* A::clone()
{
A* aa = new A();
//copy members variables to aa;
return aa;
}

A* A::clone()
{
return new A( *this );
}

is simpler and less error prone.

 

[eftewuer]

Hi, I'm trying to do something like this:

class A {
public:
virtual void f() {
// do something
}
};
class B : public A {
// some methods here
};

class C {
public:
C(A* a)
{
a_ = new WHAT?!?! // could be either A or B!!
}
A* a_;
};

In general, there could be more classes derived from A or B.... Assuming
there are copy constructors and assignment operator defined for A and B.
How can I initalize a_? do I have to resort to RTTI if-else ladders!?
There is got to be a better way!

Maybe You should write the "clone function for every class (A and B). In
class A
A* A::clone()
{
A* aa = new A();
//copy members variables to aa;
return aa;
}

In class B
B* B::clone()
{
B* bb = new B();
//copy members variables to bb;
return bb;
}

And inyour class C
C::C(A* a)
{
a_ = a.clone();
}

 

[eftewuer]

one question... does close need to be virtual? Seems like that's
necessary...

thanks.

smith.
Yes.