Overloading

This is a discussion on Overloading within the C++ Programming forums, part of the General Programming Boards category; Hi! I have a class named String which contains member "char *text" and method "void print() const;". Whenever i declare ...

  1. #1
    Code Warrior
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    Question Overloading

    Hi!

    I have a class named String which contains member "char *text" and method "void print() const;".

    Whenever i declare String class and i want to print that string on the screen i always get the address of the class String (example : 2DEE22).

    I just want to do this:

    Code:
      ...
      String s("HELLO !!");
      cout << s;
    So this must print "HELLO !!" on the screen and not "2DEE22". What I need is that cout << will automatically call print() method.

    What do I have to do to correct this problem?
    Current projects:
    1) User Interface Development Kit (C++)
    2) HTML SDK (C++)
    3) Classes (C++)
    4) INI Editor (Delphi)

  2. #2
    & the hat of GPL slaying Thantos's Avatar
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    How is String defined?
    Why are you using a non standard string class when the standard library provides one for you to use?
    Did you write a
    Code:
    friend std::ostream& operator<<(std::ostream &, const String &)
    function?
    Do you like pie?

  3. #3
    Code Goddess Prelude's Avatar
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    >How is String defined?
    Like string except with an upper case S.

    >Why are you using a non standard string class when the standard library provides one for you to use?
    For fun.

    >Did you write a <snip> function?
    I would wager not. But for grins, how about defining a
    Code:
    operator const char *() { return text; }
    member function?

    >Do you like pie?
    I like pie.
    My best code is written with the delete key.

  4. #4
    & the hat of GPL slaying Thantos's Avatar
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    Unfortuantly I think most of the people asking questions like the OP did aren't doing it for fun

  5. #5
    Code Goddess Prelude's Avatar
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    >I think most of the people asking questions like the OP did aren't doing it for fun
    What a shame, it's quite an experience. Especially if you do it right and try to meet the standard's requirements.

    That reminds me, maybe I should update my prestring class to be more l33t. It's been a while since I wrote it.
    My best code is written with the delete key.

  6. #6
    Code Warrior
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    I already have this method "operator const char *() { return text; }" and it is not working. I still get the address instead of the actual text.

    Any other suggestions?


    I like pie too .
    Current projects:
    1) User Interface Development Kit (C++)
    2) HTML SDK (C++)
    3) Classes (C++)
    4) INI Editor (Delphi)

  7. #7
    Code Goddess Prelude's Avatar
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    >and it is not working
    You aren't doing something right then. But that's a moot issue anyway because using an implicit conversion overload is fraught with danger (and everyone knows that you can't argue with a statement that uses the word fraught).

    >Any other suggestions?
    Overload the << operator as Thantos suggested.
    My best code is written with the delete key.

  8. #8
    Code Warrior
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    How am I supposed to define that friend method in .cpp file?
    Current projects:
    1) User Interface Development Kit (C++)
    2) HTML SDK (C++)
    3) Classes (C++)
    4) INI Editor (Delphi)

  9. #9
    Code Goddess Prelude's Avatar
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    >How am I supposed to define that friend method in .cpp file?
    Your best bet would be to generalize print() for all output streams, then you can do this:
    Code:
    ostream& String::operator<< ( ostream& out, const String& s )
    {
      s.print ( out );
      return out;
    }
    My best code is written with the delete key.

  10. #10
    & the hat of GPL slaying Thantos's Avatar
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    Psst Prelude the function should be:
    Code:
    ostream& operator<< ( ostream& out, const String& s )
    {
      s.print ( out );
      return out;
    }
    since its a friend function and not a member function.

    And your right there is no way to argue with fraught

  11. #11
    Code Goddess Prelude's Avatar
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    >Psst Prelude the function should be
    Shh! If you don't say anything then maybe nobody will notice.

    >And your right there is no way to argue with fraught
    My code is fraught with perfection. If it looks wrong then that's only because, in my awesomeness, I anticipated a future addition to the language and started using it. Yea, that's it. I'm so awesome that I can predict the tides of ISO! Hahaha! Make way for my head!
    My best code is written with the delete key.

  12. #12
    & the hat of GPL slaying Thantos's Avatar
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    This just in: Prelude's head has been entered into the Macy's Thanksgiving Day Parade. She is expected to win best ballon.

  13. #13
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    My prof is all against friend functions, He claims they break encapsulation and make code hard to debug.

    He suggests using accessor functions to manipulate the class.

    I am refering to overloading << and >> mainly.

    He made a good argument and it has made me rethink my method of overloading the ostream operators.

  14. #14
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    Quote Originally Posted by curlious
    My prof is all against friend functions.
    Probably he says also that void main is ok....
    As far as I know, friend functions are defined by who creates the class, therefore the encapsulation argument, for me, is non-sense.

    GaPe, those strange numbers are obviously memory adresses. You need some where to de-reference a pointer.
    Last edited by xErath; 11-15-2004 at 09:31 PM.

  15. #15
    Toaster Zach L.'s Avatar
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    There is good logic behind that. In general, I tend to avoid friends. If it does need access to the internals of the class, it probably should be a member.

    Here is a well articulated rant (particularly against std::string): http://www.gotw.ca/gotw/084.htm
    Last edited by Zach L.; 11-15-2004 at 09:41 PM.
    The word rap as it applies to music is the result of a peculiar phonological rule which has stripped the word of its initial voiceless velar stop.

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