Question

I am making the game Pong in Ruby using the library Gosu. Right now, I am trying to make the ball interacts with the board.

class Window < Gosu::Window
    # board size 30 X 298
    def initialize
        super 1440,720,false
        self.caption = "Pong"
        @Ball = Ball.new(self)
        @Ball.warp(720,360)
        @Board1 = Board.new(self,15,360)
        @Board2 = Board.new(self,1425,360) 
    end

    def update 
        @Ball.draw
        @Ball.move
        @Ball.bounceOffBoard(@Board1,@Board2)
       ........

At the last line, I tried to pass the field @Board1 down to another class so that the @Ball knows the cordinate of the board to see whether it should jump off. But it keep throwing me mistakes like

Pong.rb:105: formal argument cannot be a constant
    def bounceOffBoard(Board1,Board2)

What should I do?

Answer 1

For a start, don’t name instance variables with capital letters:

@Ball = Ball.new(self)
@Board1 = Board.new(self,15,360)
@Board2 = Board.new(self,1425,360) 

should be:

@ball = Ball.new(self)
@board1 = Board.new(self,15,360)
@board2 = Board.new(self,1425,360) 

And:

def bounceOffBoard(Board1,Board2)

should be:

def bounceOffBoard(board1, board2)