Is it possible to pass a class to a function?

This is a discussion on Is it possible to pass a class to a function? within the C++ Programming forums, part of the General Programming Boards category; Can i do something like: Code: class T { void doIt(SomeClass) { //call some static method on SomeClass } }; ...

  1. #1
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    Is it possible to pass a class to a function?

    Can i do something like:

    Code:
    class T
    {
         void doIt(SomeClass)
         {
              //call some static method on SomeClass
         }
    };
    
    int main()
    {
         T a;
    
         //Pass ref to the class itself, rather than an instance
         a.doIt( ::SomeClass );
    }

  2. #2
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    correct me if I am wrong, but, no, it's not javascript. (the compiler needs to know exactly which function to call in doIt(), which is not possible if it doesn't know what class is going to be passed in)

  3. #3
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    Code:
    class Someclass {
         static void method() {};
    };
    
    class T
    {
         void doIt(SomeClass &c)
         {
              //call some static method on SomeClass
              c.method();
         }
    };
    
    int main()
    {
         Someclass d;
         T a;
    
         //Pass ref to the class itself, rather than an instance
         a.doIt( d );
    }
    Last edited by robwhit; 05-01-2008 at 04:25 PM. Reason: all-important typo :D

  4. #4
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    Quote Originally Posted by robwhit View Post
    Code:
    class Someclass {
         static void method() {};
    };
    
    class T
    {
         void doIt(SomeClass c)
         {
              //call some static method on SomeClass
              c.method();
         }
    };
    
    int main()
    {
         Someclass d;
         T a;
    
         //Pass ref to the class itself, rather than an instance
         a.doIt( d );
    }
    Actually, that's passing an instance from what i understand. It simply calls the () constructor (which the compiler created for you) to create "d". If you create a constructor for SomeClass with no args and put a printf in it, you'll see it's being called.

  5. #5
    Captain Crash brewbuck's Avatar
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    Code:
    class T
    {
        template <typename C>
        void doIt()
        {
            C::someMethod();
        }
    };
    
    T().doIt<SomeClass>();
    Although in this case, class T is redundant, as this could be implemented as a free function.

  6. #6
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    sorry, typo.

  7. #7
    Master Apprentice phantomotap's Avatar
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    1) Use a simple wrapper and a constant reference to that wrapper. (A class instance would not be passed, only an instance of the wrapper--which need not have a reference to the class itself.)

    2) Use a template method and explicitly pass arguments to the template parameters.

    3) Use a pointer-to-a-function and pass the static method directly.

    4) "Erase" the target function type with something like "functiods" and pass an instance of that object.

    Soma

  8. #8
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    Quote Originally Posted by brewbuck View Post
    Code:
    class T
    {
        template <typename C>
        void doIt()
        {
            C::someMethod();
        }
    };
    
    T().doIt<SomeClass>();
    Although in this case, class T is redundant, as this could be implemented as a free function.

    YES! thank you, I don't know why I didn't think of templates.

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