Question

I defined a node class and player class as following:

class Node < OpenStruct
  def initialize(parent,tag,&block)
    super()
    self.parent = parent
    self.parent.children << self unless parent.nil?
    self.children = []
    self.tag = tag
    instance_eval(&block) unless block.nil?
  end
end

class Player < Node
  def initialize(parent)
    Node.new(parent,:player) do 
      self.turn_num = 1
    end
  end
end

The instance variable player was created by

player = Player.new(room) # room is the parent node which was defined
puts player.turn_num

And I got the error:

in `method_missing': undefined method `[]' for nil:NilClass (NoMethodError)

Could you help me figure out where went wrong? Thanks!

Edit:

The problem should be the initialize in the Player class. I changed my codes

class Player < Node
      def self.new(parent)
        Node.new(parent,:player) do 
          self.turn_num = 1
        end
      end
 end

Then there is no error.What’s wrong with the initialize here?

Answer 1

You don’t need to initialize a Node inside Player, because any Player instance is already also a Node instance. Instead, you should pass the expected arguments into super:

class Player < Node
  def initialize(parent,&block)
    super(parent, :player, &block)
    self.turn_num = 1
  end
end

Generally, it’s a bad idea to override .new – this is defined by default for all Ruby objects to allocate memory and then run the initialize method (if it exists). When you override it as self.new, you’re just returning a bare Node instance, not a Player instance.