include

Hello.

I'm building a program with 4 classes:
1) Abtract-Base class - Father
2) Inherit Class - A
3) Inherit Class - B
4) Inherit Class - C

I need A, B and C to include each other headers, but I seem to have some problem, probebly with has to do with all 3 classes including each other (tought I have #ifndef and #define in each header).

Solution anyone? I'm quite helpless...

If the classes only need to know that the name of the siblings exist - only use references/pointers to refer to those - then those headers are not included in headers and forward declarations are used instead.

Code:

---

//a.h
...
class B;
class A
{
    ...
    void foo(const B& b);
};

//a.cpp
#include "a.h"
#include "b.h" //for full type
void A::foo(const B& b) {...}

---

If they actually want to declare instances of those, you are probably screwed.

Quote:

---

Originally Posted by anon

If they actually want to declare instances of those, you are probably screwed.

---

That means you have to rethink your design ;)

I'm almost there...

Say I don't have any .cpp files. All implementation are in the headers.
Now in header B I have an object name some_obj typed A*, and I want to call
some_obj->print().
How do i make the call syntaxly? A::some_obj->print () doesn't work...

As you normally would,
some_obj->print();
Assuming you've included the header and the compiler can see the object whose member function you want to call.
Unless it's inside a namespace (or is a static member of a class) named A, which would make your above syntax correct.

It doesn't work. for some reason the compailer claims "use of undefined type 'A'" when I tyr to call some_obj->print();


I'm soon to be out of my mind... anyone????

You haven't included the appropriate header for the definition of the class or type A (or you have circular references [A including B and B including A]).

You have to use cpp files, at least for functions that use the forward declared names. The thing is that the declarations must not know the full type of other classes (in this case - because this would create circular dependencies) but the implementations do.

The thing is i'm implementing an operator so I can't do it in a .cpp file, can I???

Unless you are using templates, you can.
Even if you are using templates, however, you can still split the definition and the implementation.

For multiple dispatch you only need forward declarations. You shouldn't need anything more to implement the problem from your other thread.

The reason is that the operators you are defining should take references to const, and a reference requires only a forward declaration.

Then, after all your classes are defined, you can implement the operator functions.