Question

i want to run the function Run in the main, but am not allowed to create object due to no default constructor. when i try to create the default constructor, i receive the message, ‘Error”Game::Game int maxComponents)” provides no initialiser for:’

//Game.h 
#pragma once
#include "GameComponent.h"
#include <time.h>
class Game
{
private:
    int componentCount;
    GameComponent** components;
    const int TICKS_1000MS;
public:

    Game(){}    //this does not work either
    Game(int maxComponents){}   //this does not work as my default constructor
    ~Game();
    void Add(GameComponent*);
    void Run();

};

//Game.cpp
#pragma once
#include "StdAfx.h"
#include "Game.h"
#include <iostream>
#include<time.h>
using namespace std;


void Game::Add(GameComponent*)
{
    components= new GameComponent*[componentCount];


}
void Game::Run()
{

    time_t rawtime;
    struct tm * timeinfo;

    time ( &rawtime );
    timeinfo = localtime ( &rawtime );      
    //cout << timeinfo->tm_hour<< ":" << timeinfo->tm_min << ":" << timeinfo->tm_sec << endl;

    for(int n=0;n<componentCount;n++)
    {
        components[n]->Update(timeinfo);

    }
}


Game::~Game()
{
}


//main.cpp
#include "stdafx.h"
#include <iostream>
#include "Game.h"
#include <time.h>

using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
    Game obj1;
    obj1.Run();
    system("pause");
    return 0;
}

So, how do i create a default constructor here? i’ve tried to use member initialising too, doesn’t work. and copy constructor.

Answer 1

A default constructor is a constructor that takes no arguments. So, you should declare a constructor that looks something like this:

Game() { }

You can keep your other constructor – normal function overloading applies to constructors, so it will use your Game(int) constructor when you specify a single integer argument, and Game() when you specify no arguments.

However, in your case Game contains a const int member (TICKS_1000MS). Since it’s const, it’s expected to be initialized in the constructor. So you should do something like this:

Game() : TICKS_1000MS(123) { } // replace 123 with whatever the value should be

You need to do that for all constructors.

It’s a little silly to have a non-static const member of a class which is always initialized to the same value (as opposed to a value passed in as an argument to the constructor). Consider making it an enum instead:

enum { TICKS_1000MS = 123 };

or, a static const member:

static const int TICKS_1000MS;

and initialize it in Game.cpp:

const int Game::TICKS_1000MS = 123;