How can I use Objects form main in any class? C++

Question

Can anyone tell me how I can use object that I defined in main like this

int main()
{
sf::RenderWindow window;
}

And now I want to use window object in class that I made. But it must point out to the same main's window. How can we use it? Can anyone explain it with some code example?
I am using SFML library of C++.

Time to read a good C++ book: http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list — John Dibling, Jan 13 '14 at 17:14

score 2 · Accepted Answer · answered Jan 13 '14 at 17:09

2

You can pass them as references or pointers, ex.:

class CEngine {
  sf::RenderWindow& window;
public:
  CEngine(sf::RenderWindow& wnd) : window(wnd) {}
  // ...
};

int main()
{
sf::RenderWindow window;
CEngine engine(window);
}

answered Jan 13 '14 at 17:09

marcinj

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Can you please explain 4th line of your code? Under `public` ? – Max Daniel Jan 13 '14 at 17:11
This is constructor, with parameter of type reference to `sf::RenderWindow`. If you have reference field (variable) in your class you must initialize it in constructor initialization list, that is `window(wnd)`. – marcinj Jan 13 '14 at 17:15
Why did you make constructor in private. Why not public? – Max Daniel Jan 13 '14 at 17:37
It is in public, everything below `public:` is public. – marcinj Jan 13 '14 at 17:41
Oh sorry I didn't see! – Max Daniel Jan 13 '14 at 17:43
Well Thanks! I got it! – Max Daniel Jan 13 '14 at 17:43

score 1 · Answer 2 · answered Jan 13 '14 at 17:11

There are several solutions to making objects created in main available to other code:

Pass the window as a parameter, by pointer or by reference, to code that needs to use it
Make a singleton object that holds a pointer to the window, use that object throughout your code, and set its pointer in main before calling any other code
For the sake of completeness, you can make a global variable pointing to your object in main. This is not a good recommendation.

How can I use Objects form main in any class? C++

2 Answers2