Thread: Base Class Undefined

  1. #1
    Registered User
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    Dec 2003

    Base Class Undefined

    I am working on a project, and am getting the base class undefined error. I have one class in one header, and another class in another header. The second class inherits from the first. I made a seperate project, and it worked fine. I have been looking for quite awhile now on how to fix this, and can't find anything that works. I have tried declaring the base class(ex: Class Unit before the inheriting one, and I am positive the includes are all there. Is there something about compiler options I should know to fix this? Is there a way to set the order in which things are compiled?

    Thnaks for any help,


  2. #2
    C++ Developer XSquared's Avatar
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    Jun 2002
    Ontario, Canada
    Which compiler?
    Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah

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  3. #3
    Programming Sex-God Polymorphic OOP's Avatar
    Join Date
    Nov 2002

    Re: Base Class Undefined

    Originally posted by Khelder
    I am working on a project, and am getting the base class undefined error.
    Because you are only exposing your child class to the declaration of the class instead of the definition.

    class A;
    class B : A {};
    is not enough information for inheritance. class B needs to know what class A is. If you are including the file with A's definition, then make sure that you don't have class A's file including class B's file (or class A's file includes a file which includes class B's file). If you do and the translation unit you are currently in includes file A before it includes file B and you have inclusion guards, then when class B gets compiled it will not have access to class A's definition. Hence you get a base class undefined error.

  4. #4
    Registered User
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    Dec 2003
    Ah cool. Thanks for clearing that up for me. Works now!


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