as a reference would be one way
that's just pseudo javaish code.
class Main {
private playerMap: playerMap;
public void main(args[]) {
final child ChildClass = new ChildClass(this.playerMap);
child.doSomethingWithPlayers();
}
}
the main thing about object orientation is control over the messaging "what gets passed to whom and how can it be accessed".
there are different patterns to work with but passing a reference is an easy approach.