C++ Polymorphism error: no matching function for call to

Question

I'm trying to pass a child object to a function that accepts its parent object with the code:

Rook bRookL();
board[0][0].setPieceObj(bRookL);

and I get the following errors:

    ChessBoard.cpp:16:35: error: no matching function for call to 'Space::setPieceObj(Rook (&)())'
     board[0][0].setPieceObj(bRookL);
                                   ^
In file included from ChessBoard.h:13:0,
                 from ChessBoard.cpp:5:
Space.h:62:10: note: candidate: void Space::setPieceObj(Piece&)
     void setPieceObj(Piece &);
          ^
Space.h:62:10: note:   no known conversion for argument 1 from 'Rook()' to 'Piece&'

Here is my code:

ChessBoard.h:

#ifndef CHESSBOARD_H
#define CHESSBOARD_H

#include "Space.h"

using namespace std;

class ChessBoard {

private:
    Space board[8][8]; // board[0][0] is the upper-left corner of the board and
                       // board[7][7] is the lower-right corner of the board

public:
    ChessBoard();

};

#endif /* CHESSBOARD_H */

ChessBoard.cpp:

#include "ChessBoard.h"
#include "Space.h"
#include "Rook.h"

using namespace std;

ChessBoard::ChessBoard() {

    Rook bRookL();
    board[0][0].setPieceObj(&bRookL);

}

Rook.h:

#ifndef ROOK_H
#define ROOK_H

#include "Piece.h"

using namespace std;

class Rook : public Piece {

public:
    Rook() : Piece() {

    }

};

#endif /* ROOK_H */

Piece.h:

#ifndef PIECE_H
#define PIECE_H

using namespace std;

class Piece {

public:
    Piece() {

    }

};

#endif /* PIECE_H */

Space.h:

#ifndef SPACE_H
#define SPACE_H

#include "Piece.h"
#include "Rook.h"

using namespace std;

class Space {

private:
    Piece *pieceObj;

public:
    void setPieceObj(Piece &);

};

#endif /* SPACE_H */

Space.cpp:

#include "Space.h"

using namespace std;

Space::Space() {



}

void Space::setPieceObj(Piece &p) {

    pieceObj = p;

}

Please help. Thanks.

score 4 · Accepted Answer · answered Jun 03 '16 at 02:19

4

It appears, based on the examination of your code, that setPieceObj() should probably take a pointer argument:

void Space::setPieceObj(Piece *p) {

    pieceObj = p;

}

That's one problem. Now, you need to pass a pointer to a Piece object.

Rook bRookL();
board[0][0].setPieceObj(&bRookL);

That's a most vexing parse, that declares a function that returns a Rook, and passes a pointer to it, to setPieceObj().

There's not enough information to determine your clear intent. Perhaps:

Rook bRook;
board[0][0].setPieceObj(&bRookL);

answered Jun 03 '16 at 02:19

Sam Varshavchik

114,536
5
94
148

I changed Rook bRookL(); to Rook bRook; and then changed Piece *pieceObj; to Piece pieceObj; and it compiles. Thank you! – Daniel Gilbert Jun 03 '16 at 02:34
1

Eh, not so fast, @user3706950. You need to use pointers. Otherwise you're going to have an [object slicing problem](http://stackoverflow.com/questions/274626/what-is-object-slicing). – Sam Varshavchik Jun 03 '16 at 02:39
I will probably use pointers instead, now that I just realized bRookL will go out of scope when the function ends. – Daniel Gilbert Jun 03 '16 at 02:43
Interesting post on object slicing. Thanks for the info! – Daniel Gilbert Jun 03 '16 at 03:00

songyuanyao · Answer 2 · 2016-06-03T02:25:23.417

Rook bRookL();
board[0][0].setPieceObj(&bRookL);

1.Rook bRookL(); doesn't do what you expect, it's a declaration of function , which takes no parameters and returns Rook, i.e. Rook (*)() (just as compiler told you).

2.&bRookL will return the address of bRookL, so it will be a pointer. But Space::setPieceObj(Piece &p) expects its paramter to be Piece&. It seems you should change the parameter type to Piece* to make them consistent.

Then

Rook bRookL;
board[0][0].setPieceObj(&bRookL);

score 1 · Answer 3 · answered Jun 03 '16 at 02:20

Pointer (&bRookL) can't be cast to reference (Piece&).

Most likely solution is in declaration of setPiece that should take pointer:

void setPieceObj(Piece*);

Which should actually make definition to be compilable too:

void Space::setPieceObj(Piece* p) {
    pieceObj = p;
}

C++ Polymorphism error: no matching function for call to

3 Answers3