c++ “Incomplete type not allowed” error accessing class reference information (Circular dependency with forward declaration)

Question

Had some issues in my code recently surrounding what I now know of as a Circular dependency. In short there are two classes, Player and Ball, which both need to use informat

Answer 1

Player.cpp require the definition of Ball class. So simply add #include "Ball.h"

Player.cpp:

#include "Player.h"
#include "Ball.h"

void Player::doSomething(Ball& ball) {
    ball.ballPosX += 10;                   // incomplete type error occurs here.
}