struct error "uninitialized reference member"

Question

im a noob especially in c++.

I have some problems using a struct that i want to use in some functions.

I looked at the other answers here regarding structs in Header files and .cpp but dont realy get it to work.

my .h file:

namespace game {

class CPlayer{

        struct GameData{
        int mBoard[8][8];
        CBoard &pBoard;
    };
public:

    CMove Play(const CBoard &pBoard,const CDeadline &pDue);

private:

    int GainsFromMoves(struct GameData gameData);

etc.....

then in my .cc file im trying to use this data with:

CMove CPlayer::Play(const CBoard &pBoard,const CDeadline &pDue)
{

     GameData gameData;

     gameData.pBoard = pBoard;

etc...

where i try to declare the GameData i get an error uninitialized reference member in ‘struct game::CPlayer::GameData’

later trying to usethe GainsFromMoves function i also get some error.

int GainsFromMoves(GameData gameData){

 int test = 0;

 return test;
}

error: Multiple markers at this line
    - expected ‘,’ or ‘;’ before ‘{’ token
    - ‘GameData’ was not declared in this 
     scope

i realize that i probably am doing some really noob error but, i would be very happy for some guidance.

A reference member must be initialized in member initializer list. — Alok Save
– Alok Save, Commented Sep 12, 2012 at 7:02
In general, try to narrow your problems down. This has nothing to do with headers and cc. files, which you would have found out by making a five-line test program to reproduce the problem. — juanchopanza
– juanchopanza, Commented Sep 12, 2012 at 7:09
I think it's quite possible your code is confused, and that what you are trying to achieve is actually quite a long way from what you have currently. But as a first step I would move the declaration of GameData outside of the declaration of CPlayer, i.e. struct GameData { ... }; class CPlayer { ... };. Is there any reason you declared one inside the other? I would also drop completely namespace game .... At your level of understanding it's just going to make things more complicated without providing any benefit. — john
– john, Commented Sep 12, 2012 at 7:10
The second error is because compiler does not know the type, GameData.You need to include the header file which defines GameData in the source file where you have defined the function GainsFromMoves(). — Alok Save
– Alok Save, Commented Sep 12, 2012 at 7:10
I think @juanchopanza advice is good. You need to start again, build up your code slowly, adding tiny bits at a time, making sure it at least compiles as you go. Seems to me you are trying too much too quickly. — john
– john, Commented Sep 12, 2012 at 7:15

juanchopanza · Accepted Answer · 2012-09-12 07:31:24Z

2

OK, first, you need declarations of CMove, CBoard and CDeadline. I added some dummy ones to allow fixing the other problems:

namespace game {

struct CBoard {};
struct CDeadline {};
struct CMove {};
...

Then, your struct CPlayer::GameData needs to intialize it's CBoard reference, which should be const:

class CPlayer{

        struct GameData
        {
          GameData(const CBoard& board) : pBoard(board) {}
          int mBoard[8][8];
          const CBoard &pBoard;
        };
public:
    CMove Play(const CBoard &pBoard,const CDeadline &pDue);
private:
    int GainsFromMoves(struct GameData gameData);
};

Next, in your .cc file, you need the namespace as well as the class name when defining member functions:

namespace game
{
CMove CPlayer::Play(const CBoard &pBoard,const CDeadline &pDue)
{
     GameData gameData(pBoard);
     return CMove();
}
int CPlayer::GainsFromMoves(GameData gameData){

  int test = 0;

 return test;
}

} // namespace game

This gets rid of the errors, at least with this simple main:

int main()
{
  game::CBoard b;
  game::CDeadline d;
  game::CPlayer p;
  p.Play(b, d);
}

answered Sep 12, 2012 at 7:31

juanchopanza

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4 Comments

john Over a year ago

This assumes that his design is basically correct, and all that the OP needs is advice with the technical aspects of implementing it. I'm not sure that is correct. But a very useful answer if it's what the OP needs.

juanchopanza Over a year ago

@john You are right, I am not going into the design at all. I think there isn't enough information in the question yet. A lot of the code I posted is just dummy code to make things compile.

user1497664 Over a year ago

Thanks that helped but im still at square one(the reason i started all this mess with struct) When writing like you it works in my play function but in my GainsFromMoves i get errors. so in the header it is: int GainsFromMoves(struct GameData gameData); in the .cc file its: int GainsFromMoves(GameData gameData) but then i get the following : Multiple markers at this line - ‘GameData’ was not declared in this scope - expected ‘,’ or ‘;’ before ‘{’ token - Type 'GameData' could not be resolved

user1497664 Over a year ago

Hmm well moved the struct to declare it in the .cc file, combined with some of your help it made it compile at least, now i will try to see if it works as well. Again thanks

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