Passing variables between classes in Ruby

Question

I am trying to figure out how to pass variables between classes in Ruby. The example I am working on now is a game, where the players health, equipment, etc keeps changing and is passed from scene to scene until the game is over. Here is what I have so far:

class Player
  def enter()
  end
end

class MyPlayer < Player
  def initialize()
    dog_biscuits = false
  end
end

class Scene
  def enter()
  end
end

class Entrance < Scene
  def enter(player)
    puts "You are in the entrance"
    if player.dog_biscuits == false
      puts "You don't have any biscuits."
    end
  end
end

player = MyPlayer.new
entrance = Entrance.new
entrance.enter(player)

Whenever I run this, I get the following error message:

entrance.rb:20:in `enter': undefined method `dog_biscuits' for #<MyPlayer:0x007fbfe2167f20> (NoMethodError)

I am running ruby 2.2.3p173 on OSX El Capitan.

The "passing around" bit is working fine. You just messed up the `dog_biscuits` part. In your code it's a local variable. And you mean for it to be an `attr_accessor`. Google up some example for this keyword. — Sergio Tulentsev, Dec 08 '15 at 13:00

score 0 · Answer 1 · answered Dec 08 '15 at 13:05

Do this:

class MyPlayer < Player
  attr_accessor :dog_biscuits
  def initialize()
    @dog_biscuits = false
  end
end

Using attr_accessor will allow you to set and get instance variables. Remember also that you have to prefix instance variables with @.

score 0 · Answer 2 · answered Dec 08 '15 at 13:05

class MyPlayer < Player

  def initialize()
    @dog_biscuits = false
  end

  def has_no_dog_biscuits?
    @dog_biscuits == false
  end
end

It is better to create method has_no_dog_biscuits? then to have attr_reader and to expose attribute to outer world, this way, you can always check if player has not dog_biscuits.

Passing variables between classes in Ruby

2 Answers2