Inheritence, mix-ins, composotion

animal.rb

# Composition

class Eat
  def do_it
    puts 'Nom, nom ...'
  end
end

class Say
  def do_it
    puts '...'
  end
end

class Fly
  def do_it
    puts 'Flap, flap with wings and fly away ...'
  end
end

class Swim
  def do_it
    puts 'Blub, blub. Swim, swim away ...'
  end
end

class Walk
  def do_it
    puts 'Schlurf, schlurf. Walk, walk away ...'
  end
end

class Cannot
  def do_it
    fail "Sorry I can't :'("
  end
end

class Bird < Struct.new(:fly, :eat, :walk, :swim)

end

class Robin < Bird; end
class Crow < Bird; end

class Duck < Bird
  def initialize
    super(Fly.new, Eat.new, Walk.new, Swim.new)
  end
end

class Hawk < Bird
  def initialize
    super(SuperFly.new, Eat.new, Walk.new, Cannot.new)
  end
end

class Ostridge < Bird
  def initialize
    super(Cannot.new, Eat.new, Run.new, Cannot.new)
  end
end

class Turkey < Bird
  def initialize
    super(Cannot.new, Eat.new, Walk.new, Cannot.new)
  end
end

class Penguin < Bird
  
end


# duck = Duck.new; duck.fly.do_it; duck.eat.do_it; duck.walk.do_it; duck.swim.do_it

turkey = Turkey.new
turkey.walk.do_it rescue $! # => nil
turkey.fly.do_it   rescue $! # => #<RuntimeError: Sorry I can't :'(>
turkey.swim.do_it rescue $! # => #<RuntimeError: Sorry I can't :'(>

# >> Schlurf, schlurf. Walk, walk away ...