understanding inheritance

[fstigre]

Hi,

I currently practicing inheritance and I would like to understand how it works because is not working as expected.

What I have is two classes, Animal and Dog. In the code below I'm inheriting Animal to Dog and it works fine but when I try to do the oposite basically inherit Dog to Animal it doesn't work.

Can someone explain me why it doesnt work when trying to inherit atributes from Dog to Animal?

animal.h file

class Animal
{
public:
	void eat();
};

dog.h file

class Dog: public Animal
{
public:
	void bark();
};

animal.cpp file

#include <iostream>
#include <string>
#include "animal.h"
#include "dog.h"

using namespace std;

void Animal::eat()
{
	cout<<"Eating"<<endl;
}

dog.cpp file

#include <iostream>
#include <string>
#include "animal.h"
#include "dog.h"

using namespace std;

void Dog::bark()
{
    cout<<"Barking "<<endl;
}

main.cpp file

#include <iostream>
#include <string>
#include "animal.h"
#include "dog.h"

using namespace std;

int main()
{
    Animal cat;
    Dog doggy;
    cat.eat();
    doggy.bark();
    doggy.eat();
    return 0;
}

All of the code above works fine, again the problem is when I try to inherit Dog into Animal like...

This DOESN'T work

class Animal: public Dog
{
public:
	void eat();
};

Thanks a lot!

[atrium]

 

[fstigre]

Animal is the parent of Dog. That's ok.

Well, it doesn't work.

But now you are attempting to say that Animal is a child of Dog. Rather like saying a child is its own grandparent.

I'm just practicing

Thanks for your reply.

[codekiddy]

fstigre,
choose between 2 options:
1.Dog is child of animal
2.Animal is child of dog.

they can't be parent's of each other and childs ofeach other LOL.

it the same as if you would say my parents are my parents but they are also my childs, does that make any sence to you?

[fstigre]

Ok, I think I there is some confusion here, I'm only trying to inherit one at a time, thats why my confusion, why I can do it with one but not with the other.

I know the names I'm using dont make too much sense but I'm just practicing!

Thanks

[hanst99]

What exactly doesn't work?

[codekiddy]

I know the names I'm using dont make too much sense but I'm just practicing!

The names you are using are just fine, but the problem is following:

One class can not inherit another class if that class does not see the actuall delaration of the class being inherited (I hope I got that English right)

The second prblem is that you also have to use include quards.

[fstigre]

One class can not inherit another class if that class does not see the actuall delaration of the class being inherited (I hope I got that English right)

Where do I need to do the declaration?

[codekiddy]

For example like that:

#pragma once
#include "dog.h"

class Animal 
      : public Dog
{
public:
       void eat();
};

I would recommend you to learn about classes without inhritance first, also learn about organization of project files before you even thing about inheritance.

You'll just get confuzed.

[fstigre]

I found my problem, apparently the order of your includes determines who is the parent, I just moved the include for the dog.h to be before animal.h and it now works, of course now animal wont be able to inherit from dog which is totally fine, I was just trying to find the problem.

To answer my question, whichever class is included first it's the parent and any class included after can inherit from it, right?

Again the original question was:

What I have is two classes, Animal and Dog. In the code below I'm inheriting Animal to Dog and it works fine but when I try to do the oposite basically inherit Dog to Animal it doesn't work.

Sorry for the confusion.

[hanst99]

To answer my question, whichever class is included first it's the parent and any class included after can inherit from it, right?

No it's not. but C++ compilers do no lookaheads on names, so if you want to declare your class as inheriting from another one, that classes name (and declaration) already has to be known at that point.