Garden.rb

# We create a new class with some sane defaults

class Garden
  def initialize(args={})
    @trees     = args[:trees] || 15
    @perimiter = args[:perimiter] || 'fence'
    @lawn      = args[:lawn] || 'grass'
  end
end

>> Garden.new({ trees: '20' })
# { :trees => 20, :perimiter => 'fence', :lawn => 'grass' }

SmallGarden.rb

# Someone subclasses Garden and adds specializations, calling on super to use
# the sane defaults from the parent class.

class SmallGarden < Garden
  def initialize(args)
    @ornaments = args[:ornaments]
    super(args)
  end
end

>> SmallGarden.new({ ornaments: 'Gnomes' })
# { :ornaments => 'Gnomes', :trees => 15, :perimiter => 'fence', :lawn => 'grass' }

SuperSmallGarden.rb

# Then some time later a new team member subclasses Garden but forgets
# to call on super in the initialize. How would you safe-guard this?

class SuperSmallGarden < Garden
  def initialize(args)
    @catflap = args[:catflap]
  end
end

>> SuperSmallGarden.new({ catflap: false })
# { :catflap => false, :trees => nil, :perimiter => nil, :lawn => nil }