TICPP and const issues

This is a discussion on TICPP and const issues within the C++ Programming forums, part of the General Programming Boards category; I'm getting this error: Game.cpp:416: error: passing ‘const Coach’ as ‘this’ argument of ‘const std::string Person::getName()’ discards qualifiers Code: ticpp::Element ...

  1. #1
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    TICPP and const issues

    I'm getting this error:
    Game.cpp:416: error: passing ‘const Coach’ as ‘this’ argument of ‘const std::string Person::getName()’ discards qualifiers
    Code:
    ticpp::Element Game::toXML() const {
    
      Team* home=homeTeam;
      Team* away=awayTeam;
    
      ticpp::Element game=("Game");
      game.SetAttribute("location",location);
    
      //Home Team Elements
      ticpp::Element homeTeamElement("HomeTeam");
      ticpp::Element homeCoach=("Coach");
      
    
      //Coach Elements
      //Coach Attributes
    
      //ERROR IS HERE
      homeCoach.SetAttribute("name", (home->getCoach())->getName());
    
      homeTeamElement.InsertEndChild(homeCoach);
    home is a pointer, getCoach() returns a const Coach* const, and getName() returns a const string.

    If I remove all the consts, it works fine, but I need the consts.

    Any help would be great.

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    Can you declare getName as a const function? (The name suggests you can.)

  3. #3
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    Code:
     const string Person::getName(){
    	const holder=name;
    	return holder;
    }

  4. #4
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    Code:
    const string Person::getName() const{
    	const holder=name;
    	return holder;
    }
    This works. I thought the const after the function dealt with the pointer, not the function itself.

  5. #5
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by TIMBERings View Post
    Code:
    const string Person::getName() const{
    	const holder=name;
    	return holder;
    }
    This works. I thought the const after the function dealt with the pointer, not the function itself.
    You don't really have a pointer (unless you mean the this pointer?) here at all, so I have no idea where you were headed. (And if you do mean the this pointer, then you are right in practice at least -- putting a const there means the this pointer can be a const pointer.)

  6. #6
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    I know there's not a pointer in this one. That's why I hadn't put const at the end of the declaration, because I thought it only applied to pointers.

  7. #7
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    While we're at it, along the same lines:

    Team.cpp:47: error: passing ‘const std::map<int, Player, std::less<int>, std::allocator<std::pair<const int, Player> > >’ as ‘this’ argument of ‘_Tp& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const _Key&) [with _Key = int, _Tp = Player, _Compare = std::less<int>, _Alloc = std::allocator<std::pair<const int, Player> >]’ discards qualifiers
    Code:
    map<int, Player> players;
    
    const Player* Team::getPlayer(int number) const{
      
      map<int,Player>::const_iterator it;
      it=players.find(number);
      if (it!=players.end()){
    
        //ERROR HERE
        const Player* const playerPtr=&players[number];
        
        return playerPtr;
      }
      else {
        return NULL;
      }
    }
    I can't declare player as a const because I need to add to it later.

  8. #8
    and the Hat of Guessing tabstop's Avatar
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    I take it players is a member of Team? If so, then you can't use [], since that's not a const function/operator (since you use [] to add to a map). On the other hand, I don't know that you need to go to all that trouble, since it points to the element you want; why not
    Code:
    return &(*it);
    ?

  9. #9
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    I finished with this, and it compiled. Now I just hope it gets me what I want;
    Code:
    const Player* Team::getPlayer(int number) const{
      map<int,Player>::const_iterator it;
      it=players.find(number);
      if (it!=players.end()){
        const Player* const playerPtr=&((*it).second);
        return playerPtr;
      }
      else {
        return NULL;
      }
    }
    Thank you.

  10. #10
    C++ Witch laserlight's Avatar
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    I suggest that you write it in this way instead:
    Code:
    const Player* Team::getPlayer(int number) const {
        map<int,Player>::const_iterator it = players.find(number);
        if (it != players.end()) {
            return &it->second;
        }
        else {
            return NULL;
        }
    }
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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