CODEWITHSUNDEEP
c++inheritanceheader
octref
octref

Reputation: 6801

C++ Include two classes that derive from the same base class

I have a Base class Base.
Two classes that derive from it: DerivedA and DerivedB. In headers of both classes I included Base.h.
Then, in my source.cpp where I define my main, if I ONLY include DerivedA.h, it works fine. If I ONLY include DerivedB.h it also works fine. The problem is that I can't include BOTH.
Whenever I include both, the compiler generate a bunch of errors like

I guess the problem is that when I include both header, the Base.h is included twice. How should I include these headers?

Upvotes: 2

Views: 2613

Answers (2)

sircodesalot
sircodesalot

Reputation: 11439

If the problem is just the header file and not a case of the deadly diamond of death, you could just use #pragma once in your header file and that will ensure it's only ever linked once during the build process.

Alternatively, you could wrap your header file in something like this:

#ifndef HEADER_H_
#define HEADER_H_

// The content of the header file goes here...

#endif

By using pre-processor #ifXXXX statements, you can tell the compiler to only include the file if a macro is not already pre-defined.

Upvotes: 7

John Yang
John Yang

Reputation: 577

When you are inheriting from two classes which are from the same base, you should try to use the keyword "virtual" when doing the inheritance. It helps you to solve the confusion in the virtual table I believe. Look up virtual inheritance for examples.

Upvotes: -1

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