C++ Interface

This is a discussion on C++ Interface within the C++ Programming forums, part of the General Programming Boards category; Hello everyone, Just wondering how COM implementation uses keyword interface without compile error, for a normal C++ project, if we ...

  1. #1
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    C++ Interface

    Hello everyone,


    Just wondering how COM implementation uses keyword interface without compile error, for a normal C++ project, if we use keyword interface, there will be compile error.

    Code:
    interface IFoo {
    	
    	int func() = 0;
    };
    Compile error:

    --------------------
    1>d:\visual studio 2008\projects\test_virtual1\test_virtual1\main2.cp p(1) : error C2146: syntax error : missing ';' before identifier 'IFoo'
    1>d:\visual studio 2008\projects\test_virtual1\test_virtual1\main2.cp p(1) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
    1>d:\visual studio 2008\projects\test_virtual1\test_virtual1\main2.cp p(1) : error C2470: 'IFoo' : looks like a function definition, but there is no parameter list; skipping apparent body
    --------------------

    Any ideas?


    thanks in advance,
    George

  2. #2
    Jack of many languages Dino's Avatar
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    I don't do .NET, but my beginner's C++ book has 1 age on .NET and says the MS keyword is
    Code:
    __interface
    The error messages appear to me like the interface keyword you are using is not recognized.

    Could it be?

  3. #3
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    I don't know anything about COM, but there is no interface keyword in C++. Maybe it's a Microsoft extension or a macro for something like the class keyword?

  4. #4
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    Hi Todd,


    You are doing managed C++? But I am doing non-managed C++.

    Quote Originally Posted by Todd Burch View Post
    I don't do .NET, but my beginner's C++ book has 1 age on .NET
    and says the MS keyword is
    Code:
    __interface
    The error messages appear to me like the interface keyword you are using is not recognized.

    Could it be?

    regards,
    George

  5. #5
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    Yes, cpjust!


    Interface is not a part of C++ Spec, I think Visual Studio defines it to struct.

    Quote Originally Posted by cpjust View Post
    I don't know anything about COM, but there is no interface keyword in C++. Maybe it's a Microsoft extension or a macro for something like the class keyword?

    regards,
    George

  6. #6
    Jack of many languages Dino's Avatar
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    I looked it up on MSDN. Just as I suspected - it requires two underscores in front the keyword:

    http://msdn2.microsoft.com/en-us/lib...tb(VS.71).aspx

    Todd

  7. #7
    Jack of many languages Dino's Avatar
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    See this too if you want to use the interface keyword without the two underscores:

    http://msdn2.microsoft.com/en-us/library/ms858713.aspx

  8. #8
    Jack of many languages Dino's Avatar
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    Quote Originally Posted by George2 View Post
    You are doing managed C++?
    Nope. Not me.

  9. #9
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    Thanks for your great links!


    My question is answered.

    Quote Originally Posted by Todd Burch View Post
    Nope. Not me.

    regards,
    George

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