Cross-Referencing Classes

This is a discussion on Cross-Referencing Classes within the C++ Programming forums, part of the General Programming Boards category; I have two classes: mRoom and mDoor . mRoom has an array of 10 mDoor s in it, and mDoor ...

  1. #1
    C++ Developer XSquared's Avatar
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    Cross-Referencing Classes

    I have two classes: mRoom and mDoor. mRoom has an array of 10 mDoors in it, and mDoor has 2 pointers which hold the adjacent mRooms. I can't seem to get this into code.

    NOTE: the main cpp file is just has the #include and a blank main function, with a return 0 statement.

    Here's the header file:
    Code:
    #ifndef MSOLVE_H_
    #define MSOLVE_H_
    
    class mRoom
    {
    private:
    	mDoor  exits[10];
    public:
    	mRoom( );
    	~mRoom( );
    };
    
    class mDoor
    {
    private:
    	mRoom * adjRooms[2];
    public:
    	mDoor( );
    	~mDoor( );
    };
    
    #endif
    And here are the errors:
    Code:
    --------------------Configuration: RoomMazeSol - Win32 Debug--------------------
    Compiling...
    main.cpp
    c:\c++\roommazesol\msolve.h(7) : error C2146: syntax error : missing ';' before identifier 'exits'
    c:\c++\roommazesol\msolve.h(7) : error C2501: 'mDoor' : missing storage-class or type specifiers
    c:\c++\roommazesol\msolve.h(7) : error C2501: 'exits' : missing storage-class or type specifiers
    Error executing cl.exe.
    
    RoomMazeSol.exe - 3 error(s), 0 warning(s)
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  2. #2
    Registered User Pioneer's Avatar
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    Code:
    class mRoom;
    
    class mDoor
    {
    private:
    	mRoom * adjRooms[2];
    public:
    	mDoor( );
    	~mDoor( );
    };
    
    class mRoom
    {
    private:
    	mDoor  exits[10];
    public:
    	mRoom( );
    	~mRoom( );
    };

  3. #3
    Registered User
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    Here is the problem. You declare mRoom then mDoor. Your mRoom contains mDoor information but the compiler doesn't know about mDoor yet. Your mDoor is fine because above it is the mRoom declaration. So above your mRoom you need a forward declaration that will tell the compiler "There is in fact a mDoor class". It will look like this.

    Code:
    class mDoor;

  4. #4
    C++ Developer XSquared's Avatar
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    Thanks. I got it to work using Pioneers method. MrWizards didn't.
    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

    You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie

  5. #5
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    Oops, because you aren't using a pointer in your mRoom class ( i.e. you have mDoor exits[10] not mDoor *exits[10] ) it will not work the way I suggested. I just spit the answer out a little too quickly I guess.
    "...the results are undefined, and we all know what "undefined" means: it means it works during development, it works during testing, and it blows up in your most important customers' faces." --Scott Meyers

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