nebulab_alien_talk.rb

class NilObjectUnderstadingStrategy
  def self.can_talk_to?(character)
    true
  end
end

class HumanCharacterUnderstandingStrategy
  def self.can_talk_to?(character)
    character.is_a? Human
  end
end

class AlienAndHumanCharacterUnderstandingStrategy
  def self.can_talk_to?(character)
    HumanUnderstandingStrategy.can_talk_to?(character) ||
    AlienUnderstandingStrategy.can_talk_to?(character)
  end
end

class Alien
  # yes, my variable names are very long :-
  def initialize(character_understading_strategy:, others:)
    @strategy = character_understanding_strategy
    # your standard initialization code
  end

  def can_talk_to?(character)
   @strategy.can_talk_to? character
  end
end

# example usage

# level 0
Alien.new(HumanCharacterUnderstandingStrategy)
# level 2
Alien.new(AlienAndHumanCharacterUnderstandingStrategy)
# polyglot alien no problem
Alien.new(NilObjectUnderstadingStrategy)

# git commit -m "feature/13233-make-alien-talk-to-itself: injects characters alien can talk to in initializer"