class declaration in a class, definition outside a class

Hi,
How can I define a class which I declared in other class? I have such example:

Code:

class graph
{
private:
        int     **w; // w[i][v] - the weight of the edge from vertex i to v
public:
        int     vertex_number;
        class bad_size
        {
                private:
                        int size;
                public:
                        bad_size(int);
        };
        graph(int);
        int     edge_u_v(int,int);
};

And I would like to only declare class bad_size in class graph:

Code:

class graph
{
private:
        int     **w; // w[i][v] - the weight of the edge from vertex i to v
public:
        int     vertex_number;
        class bad_size;
        graph(int);
        int     edge_u_v(int,int);
};

And define it somewhere else. I tried do this like defining methods:

Code:

class graph::bad_size { ... }

but that's wrong... How can I do that correct?
Regards.

Are you talking about defining the constructor? You wouldn't use the "class" keyword again. Just imagine how you would define it if it wasn't in another class then treat the container class as a namespace, so you would have:

Code:

graph::bad_size::bad_size() {...}

edit: I just looked at your post again, my answer applies to your first code sample and not necessarily the second. As far as the second goes. I would think that the forward declaration in the class is not sufficient to make it a sub-object of the class. If you want the one class to contain the other, then declare it as in your first example.

I will try an example though to see if it can work the second way

No, I'm talking about class. I want to declare a class bad_size in the class graph but define it somewhere else (not in the graph class)

OK I believe this is the essence of what you want:

Code:

class foo
{
public:
	class bar;
};

class foo::bar
{
	int mem;
public:
	foo::bar():mem(100){}
	int GetMem() {return mem;}
};

#include <iostream>
int main()
{
	foo::bar Abar;
	std::cout << Abar.GetMem();
	system("pause");
}

which appears to be the same as you did ... this worked for me though

Yes. Thanks a lot.

Code:

foo::bar():mem(100){}        //i think foo is a unwanted name

Originally Posted by jinhao

Code:

foo::bar():mem(100){}        //i think foo is a unwanted name

How so? or are you saying it's unnecessary? which is true, but it works either way.

Originally Posted by Darryl

How so? or are you saying it's unnecessary? which is true, but it works either way.

sorry, i made a mistake