class constants

This is a discussion on class constants within the C++ Programming forums, part of the General Programming Boards category; Hi i'm trying to create a constant variable from within my class, but i just get the error [C++ Error] ...

  1. #1
    Registered User subdene's Avatar
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    class constants

    Hi i'm trying to create a constant variable from within my class, but i just get the error
    [C++ Error] Test.h(40): E2233 Cannot initialize a class member here
    Do you have to declare 2d arrays differently from within the class?

    Code:
      static const char Test[3][20] = {{"Test1"}, {"Test2"}, {"Test3"}};
    Thanks.
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  2. #2
    stovellp
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    You cant initialise a variable inside a class.
    I'm not sure, but I think you'd have to do it in the constructor.


    Code:
    class myClass
       {
       public:
          myClass();
          const int Height;
       };
    
    myClass::myClass()
       {
       Height = 67;
       }
    But if its a static variable, you define it outside the class, like:

    Code:
    const char myClass::Test[3][20] = {{"Test1"}, {"Test2"}, {"Test3"}};

  3. #3
    S Sang-drax's Avatar
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    Originally posted by stovellp
    You cant initialise a variable inside a class.
    Yes, static const variables can be.
    Code:
    //Valid C++
    class A
    {
      static const int Test  = 1;
    };
    I'm not sure why arrays can't be initialized the same way, though.
    Last edited by Sang-drax : Tomorrow at 02:21 AM. Reason: Time travelling

  4. #4
    Programming Sex-God Polymorphic OOP's Avatar
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    Only const integers can be done like that sang-drax, nothing else.
    Last edited by Polymorphic OOP; 01-25-2003 at 06:37 PM.

  5. #5
    S Sang-drax's Avatar
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    Yes, but why are only integral basic data types allowed?
    I see no reason.
    Last edited by Sang-drax : Tomorrow at 02:21 AM. Reason: Time travelling

  6. #6
    Programming Sex-God Polymorphic OOP's Avatar
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    I wonder that same thing. Not even floating point types can be initialized in a class definition. There's probably some logical reason why they didn't, but I honestly can't think of one.

  7. #7
    Registered User subdene's Avatar
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    Hi all, thanks for your replies. I've just had to make the 2d array global, thats the only way i've managed to implement the class.
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  8. #8
    Registered User Cela's Avatar
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    >>I've just had to make the 2d array global, thats the only way i've managed to implement the class.
    Initialize the array just like you do member functions, the declaration is in the class and the definition is outside of the class with named scoping.
    Code:
    class test {
      static const char Test[3][20];
      ...
    };
    
    const char test::Test[3][20] = {"Test1", "Test2", "Test3"};
    *Cela*

  9. #9
    Registered User subdene's Avatar
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    erm.... interesting. I'll have a go at that, thanks cela.
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  10. #10
    stovellp
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    Isn't that what I said in the first place?

  11. #11
    Registered User Cela's Avatar
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    >>Isn't that what I said in the first place?
    Yep, but important concepts are best repeated. :-)
    *Cela*

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