How do I get the instance of my tiles from the game class?

Question

I have a c++ problem.

So I have a base GAME class. In this class I have an instance of the player class. I want to check this player for collision with tiles. Tiles are also stored in the game class. How do I get the instance of these tiles.

I tried passing in an instance of the game class into the constructor of the player class and accessing it that way, but no success.

So for example:

Class game()
{
     Player p(x, y);
     Tile t(x, y);

     //game loop
     p.update(); //check collision

     p.render();
     t.render();
}

Player::Player(int x, int y)
{
    this.x = x;
    this.y = y;
}

Player::update()
{
     //get an the instance of tile to check the collision
}

Answer 1

Simply pass a reference to the tile to the update function:

Class game()
{
     Player p(x, y);
     Tile t(x, y);

     //game loop
     p.update(&t); //check collision

     p.render();
     t.render();
}

Player::Player(int x, int y)
{
    this.x = x;
    this.y = y;
}

Player::update(Tile* tile)
{
     //You now have a pointer to tile
}

Answer 2

There is definitely a level of guesswork in understanding your question, but a couple things that may be of note.

1. your player has no reference to your tileset and would need to have access to it if you wanted to brute force detection - iterating through all of them and acting once you find the tile(s) she is touching.
2. your player could use space partitioning, as with a BSPTree, QuadTree or OctTree, to run queries against subsets of valid elements. You may want to reach into wikipedia for more details on this and to think through how to implement it in your context.

Both solutions would likely work, the second being a better, albeit more involved, approach.

Here is a discussion of some of the techniques used in 2D.

Hopefully this is helpful.