POOD Ch 3 Sample Code

# sample_code.rb from POOD Ch 3

# Starter 1 - Heaviliy dependent Gear class
class Gear
  attr_reader :chainring, :cog, :rim, :tire

  def initialize(chainring, cog, rim, tire)
    @chainring = chainring
    @cog = cog
    @rim = rim
    @tire = tire
  end

  def gear_inches
    ratio * Wheel.new(rim, tire).diameter
  end

  def ratio
    chainring / cog.to_f
  end
end


class Wheel
  attr_reader :rim, :tire

  def initialize(rim, tire)
    @rim = rim
    @tire = tire
  end

  def diameter
    rim + (tire * 2)
  end
end

puts "The gear is #{Gear.new(52, 11, 26, 1.5).gear_inches} inches "

# Sample 2 Less dependent

# Starter 1 - Heaviliy dependent Gear class
#  Using dependency injection
class Gear
  attr_reader :chainring, :cog, :rim, :tire

  def initialize(chainring, cog, wheel)
    @chainring = chainring
    @cog = cog
    @wheel = wheel
  end

  def gear_inches
    ratio * wheel.diameter
  end

  def ratio
    chainring / cog.to_f
  end
end

# Example 3 Two ways of isolating dependency

# class Gear
#   attr_reader :chainring, :cog, :rim, :tire
#
#   def initialize(chainring, cog, rim, tire)
#     @chainring = chainring
#     @cog = cog
#
#     # Wheel is isolated to the initialize method
#     @wheel = Wheel.new(rim, tire)
#   end
#
#   def gear_inches
#     ratio * wheel.diameter
#   end
#
#   def ratio
#     chainring / cog.to_f
#   end
# end
#
# class Gear
#   attr_reader :chainring, :cog, :rim, :tire
#
#   def initialize(chainring, cog, rim, tire)
#     @chainring = chainring
#     @cog = cog
#     @rim = rim
#     @tire = tire
#   end
#
#   # Wheel is isolated to a method
#   def wheel
#     @wheel ||= Wheel.new(@rim, @tire)
#   end
#
#   def diameter
#     wheel.diameter
#   end
#
#   def gear_inches
#     ratio * diameter
#   end
#
#   def ratio
#     chainring / cog.to_f
#   end
# end

# class Gear
#   attr_reader :chainring, :cog, :rim, :tire
#
#   # Removing order dependency by using a hash parameter
#   def initialize(args)
#     @chainring = args[:chainring]
#     @cog = args[:cog]
#     @rim = args[:rim]
#     @tire = args[:tire]
#   end
#
#   # Wheel is isolated to a method
#   def wheel
#     @wheel ||= Wheel.new(@rim, @tire)
#   end
#
#   def diameter
#     wheel.diameter
#   end
#
#   def gear_inches
#     ratio * diameter
#   end
#
#   def ratio
#     chainring / cog.to_f
#   end
# end


# Example using || for default arguments
# 
# class Gear
#   attr_reader :chainring, :cog, :rim, :tire
#
#     def initialize(args)
#       @chainring = args[:chainring] || 40
#       @cog = args[:cog] || 11
#       # Could also use args.fetch
#       # @cog = args.fetch(:cog, 22)
#       @rim = args[:rim]
#       @tire = args[:tire]
#     end
#
#     # def initialize(args)
#     #   args = defaults.merge(args)
#     #   @chainring = args[:chainring]
#     #   @cog = args[:cog]
#     #   @rim = args[:rim]
#     #   @tire = args[:tire]
#     # end
#
#     # Use when default arguments are more complicated than this!
#     # def defaults
#     #   { :chainring => 40, :cog => 18}
#     # end
#
#
#   # Wheel is isolated to a method
#   def wheel
#     @wheel ||= Wheel.new(@rim, @tire)
#   end
#
#   def diameter
#     wheel.diameter
#   end
#
#   def gear_inches
#     ratio * diameter
#   end
#
#   def ratio
#     chainring / cog.to_f
#   end
# end