variable or field declared void-error?

Ok, I'm working on a remake of the program called breakout for a school assignement and I'm getting this one error: \Squares.h variable or field `squareCollision' declared void The acctual function in the .h file is simple:

void squareCollision(Ball *ballPointer);

and the implementation in the .cpp file is:

void squareCollision(Ball *ballPointer){
  for(int i = 0; i < ROW_SIZE * COLUMN_SIZE; i++)
    {
     if(squareExists == true){        
      if(ballPointer->ballX <= highX && ballPointer->ballX >= lowX) 
      {
        if(ballPointer->ballY <= highY && ballPointer->ballY >= lowY)
        {
        squareExists = false;
        ballPointer->ballYVelocity = -ballPointer->ballYVelocity;
        ballPointer->ballXVelocity = -ballPointer->ballXVelocity;
        player1_points++;
        }
      }      
     }
    }            
}

Now I'm trying to make the squareCollision(Ball *ballPointer) function take an object of type "Ball" and pass it to the function so I can modify/access the variables in the function. Am I doing this correctly? Also, does anyong know why I might be getting that particular error?