Question

Given a class instance and a string, how do I convert the string to refer to the instance?

class Room
  def enter
    puts "Welcome!"
  end
end

# Rooms are predefined
lounge = Room.new
kitchen = Room.new
study = Room.new

puts "Which room would you like to go to?"
print "> "
room = gets.strip

# User types "lounge"

room.enter # => undefined method `enter' for "lounge":String (NoMethodError)

I understand why I’m getting NoMethodError, but I haven’t been able to work out how to convert the room string to refer to the existing instance of Room named lounge.

Answer 1

I ended up storing each Room object in a hash as a class variable on initialization. This lets you refer to each instance via the hash:

class Room
  @@rooms = {}

  def initialize(name)
    @@rooms.store name, self
  end

  def rooms
    @@rooms
  end

  def enter
    puts "Welcome!"
  end
end

# Rooms are predefined
lounge = Room.new('lounge')
kitchen = Room.new('kitchen')
study = Room.new('study')

puts "Which room would you like to go to?"
print "> "
new_room = gets.strip

lounge.rooms[new_room].enter if lounge.rooms.has_key? new_room