Inheritance and Overloading

[Larry Lindsey]

If I have classes Parent, Child, and Seat as follows

class Parent{
public:
float getValue(){return 0;}
...
}

class Child: public Parent{
public:
float getValue(){return val;}
...
private:
float val;
}

class Seat{
public:
Parent* getPerson(){
return thePerson;
}
void setPerson(Parent *inPerson){
thePerson=inPerson;
}
...
private:
Parent* thePerson;
}

If i do this:

Child *c = new Child();
Seat *s = new Seat();
Child->setValue(12);
s->setPerson(c);

How would I make s->getPerson()->getValue() return 12, and not 0?

--Larry

 

[jeffc]

If I have classes Parent, Child, and Seat as follows

class Parent{
public:
float getValue(){return 0;}
...
}

class Child: public Parent{
public:
float getValue(){return val;}
...
private:
float val;
}

class Seat{
public:
Parent* getPerson(){
return thePerson;
}
void setPerson(Parent *inPerson){
thePerson=inPerson;
}
...
private:
Parent* thePerson;
}

If i do this:

Child *c = new Child();
Seat *s = new Seat();
Child->setValue(12);

Did you forget to define this function?

s->setPerson(c);

How would I make s->getPerson()->getValue() return 12, and not 0?

Read up on virtual functions.

 

[Larry Lindsey]

Did you forget to define this function?


Read up on virtual functions.

Thanks

 

[red floyd]

Did you forget to define this function?




Read up on virtual functions.

In other words, because Parent::getValue() is non-virtual, and getPerson
returns a Parent*, any reference to getValue() through getPerson() will access
Parent::getValue().

If you declare getValue() as virtual in Parent(), then it will behave in the
polymorphic manner that you desire.

 

[Larry Lindsey]

In other words, because Parent::getValue() is non-virtual, and getPerson
returns a Parent*, any reference to getValue() through getPerson() will access
Parent::getValue().

If you declare getValue() as virtual in Parent(), then it will behave in the
polymorphic manner that you desire.

I've made everything virtual that needs to be virtual, but now I'm having a
problem where private variables aren't keeping their values. Does anyone
know whats going on?

for instance, in the above example, after I call c->setValue(12), were I to
call c->getValue(), it would return -8.4873e+008, which I'm pretty sure is
2's complement 0x000000 for some number of 0's.

Thanks for all of you help thus far, btw.