nested #includes

This is a discussion on nested #includes within the C++ Programming forums, part of the General Programming Boards category; I have two classes class a and class b I #include class a in class b anb class b in ...

  1. #1
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    nested #includes

    I have two classes class a and class b
    I #include class a in class b anb class b in class a the reason for this is that class a needs to interact with class b and vice versa. I have my #include guards in but I still get the error message #include nested too deeply. Is there a way to get around this.

  2. #2
    MFC killed my cat! manutd's Avatar
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    Give us your code.
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  3. #3
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    Code:
    #include "classb.h"
    
    #ifndef CLASS_A
    #define CLASS_A
    
    class A{
    
    public:
                .
                .
                .
    const string A_Attacks_B(classBobject&)
    
    private:
                .
                .
    };
    
    
    
    #include "classa.h"
    
    #ifndef CLASS_B
    #define CLASS_B
    
    
    class A{
    
    public:
                .
                .
                .
    const string B_Attacks_A(classAobject&)
    
    private:
                .
                .
    };

    This is the basis of my code then in main I call each function

  4. #4
    (?<!re)tired Mario F.'s Avatar
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    Is that code all inside one file?

    Anyways the type of relationship between classA and classB expressed in the member functions, const string A_Attacks_B(classBobject&) and const string B_Attacks_A(classAobject&) doesn't call for an include. A simple forward declaration will be enough.
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  5. #5
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    In fact, you should use a forward declaration for both files, since you should prefer a forward declaration over including a header.

  6. #6
    (?<!re)tired Mario F.'s Avatar
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    Also, on both classes include stataments should go after the header guards and that is the main reason why you are having errors.

    Secondly I blieve you second class sould be B, not A.
    Code:
    #ifndef CLASS_B
    #define CLASS_B
    
    
    class B{
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  7. #7
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    Thanks all that worked but now I am getting an error message that classA has not been declared

    Code:
    #ifndef
    #define
    
    #include "classb.h"
    
    class A{
    
    public:
                .
                .
                .
    const string A_Attacks_B(classBobject&)
    
    private:
                .
                .
    };
    
    
    #ifndef
    #define
    
    #include "classa.h"
    
    class B{
    
    public:
                .
                .
                .
    const string B_Attacks_A(classAobject&)
    
    private:
                .
                .
    };
    the code is seperate header files

  8. #8
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    also I did use a forward declaration but I got errors about invalid use of a struct classA or invalid use of struct classB

  9. #9
    (?<!re)tired Mario F.'s Avatar
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    > also I did use a forward declaration but I got errors about invalid use of a struct classA or invalid use of struct classB

    It's possible that you didn't tell us the whole story and the bits of code we aren't seeing make other uses of those classes. How about showing us the whole of the class definition? Or is it too big?

    > Thanks all that worked but now I am getting an error message that classA has not been declared

    What happened to the header guards?
    The programmer’s wife tells him: “Run to the store and pick up a loaf of bread. If they have eggs, get a dozen.”
    The programmer comes home with 12 loaves of bread.


    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  10. #10
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    No there are no other functions but that one that uses it it is the only instance i have of that object

  11. #11
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    You should remove #include "classb.h" and put
    Code:
    class B;
    You should do the same for class A. If you get errors doing that post your attempt and the exact errors.

    If you used struct instead of class, the compiler might complain because you use struct in one place and class in another.

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