simple constructor question

[mjl3434]

I'm writing a simple game application. A game object is composed of a Board and an AI player. When the AI player is constructed it needs a reference to a board object, so it can interact with it. How can I set up the game class so that its members get constructed properly--considering that one needs a reference to another?

class Game
{
    private:
        Board theBoard;
        AI computerPlayer;  // AI needs reference to theBoard (above)
};

class AI
{
    AI(Board& board_in) : theBoard(board_in)

    private:
        Board& theBoard;
};

[TheRogue]

Objects are constructed in the order they are declared, so could you do:


Game() : computerPlayer(theBoard) {
}


Or alternatively, have an initialisation function that takes a Board ?

[mjl3434]

When I try this there is a scope problem. I ran a simple test:

#include <iostream>

using std::cout;

class ObjectA;
class ObjectB;

class ObjectB
{
   public:
        ObjectB(ObjectA& refIn) : associatedObjectA(refIn)
        {
            cout << "Object B constructor.\n";
        }

    private:
        ObjectA& associatedObjectA;
};

class ObjectA
{
    public:
        ObjectA()
        {
            cout << "Object A constructor.\n";
        }
};

class Container
{
    public:
        Container() : theObjectB(theObjectA)
    private:
        ObjectA theObjectA;
        ObjectB theObjectB;
};

int main()
{
    Container myContainer;
    return 0;
}

And the error I get is:

t.cpp: In constructor 'Container::Container()':
Line 32: error: 'theObjectA' was not declared in this scope
compilation terminated due to -Wfatal-errors.


Is it just that what I am doing does not make sense or is not possible?

[LarryChen]

The body for container constructor is missing.

When I try this there is a scope problem. I ran a simple test:

#include <iostream>

using std::cout;

class ObjectA;
class ObjectB;

class ObjectB
{
   public:
        ObjectB(ObjectA& refIn) : associatedObjectA(refIn)
        {
            cout << "Object B constructor.\n";
        }

    private:
        ObjectA& associatedObjectA;
};

class ObjectA
{
    public:
        ObjectA()
        {
            cout << "Object A constructor.\n";
        }
};

class Container
{
    public:
        Container() : theObjectB(theObjectA)
    private:
        ObjectA theObjectA;
        ObjectB theObjectB;
};

int main()
{
    Container myContainer;
    return 0;
}

And the error I get is:

t.cpp: In constructor 'Container::Container()':
Line 32: error: 'theObjectA' was not declared in this scope
compilation terminated due to -Wfatal-errors.


Is it just that what I am doing does not make sense or is not possible?

[mjl3434]

Yes that's right. I got it working now. Thanks.