exception virtual function through base class

[voidtwerp]

The following code cant call derived::fn() , it is calling base::fn()
which is pure virtual.
(the same problem is ocurring if I do it outside of constructors also)
What am I doing wrong here?

class base
{
public:
virtual void fn(void)=0;
};

class derived
{
public:
void fn(void){};
};

class user
{
public:
user(){
derived d;
p=(base*)new derived();//What is wrong here?
if(p!=0)
p->fn();//exception because p->fn == 0
}
private:
base *p;
};

 

[TB]

voidtwerp skrev:

The following code cant call derived::fn() , it is calling base::fn()
which is pure virtual.
(the same problem is ocurring if I do it outside of constructors also)
What am I doing wrong here?

class base
{
public:
virtual void fn(void)=0;
};

class derived

class derived : public base

 

[Murali Krishna]

The following code cant call derived::fn() , it is calling base::fn()
which is pure virtual.
(the same problem is ocurring if I do it outside of constructors also)
What am I doing wrong here?

class base
{
public:
virtual void fn(void)=0;
};

class derived
{
public:
void fn(void){};
};

class user
{
public:
user(){
derived d;
p=(base*)new derived();//What is wrong here?
if(p!=0)
p->fn();//exception because p->fn == 0
}
private:
base *p;
};

you haven't inherited the base class.

p=(base*)new derived();//What is wrong here?

same as above. base and derived are two different classes with no
relation

-- Murali Krishna

 

[voidtwerp]

you haven't inherited the base class.

doh! thanks to TB and Murali for your quick responses - how I managed
to do that in both the original problem and the posted version without
spotting it I dont know.

 

[Pete Becker]

doh! thanks to TB and Murali for your quick responses - how I managed
to do that in both the original problem and the posted version without
spotting it I dont know.

The cast was a clue. (I missed it, too, on my first reading)