POODR: Chapter 7 - Sharing Role Behavior With Modules

Chapter_7.rb

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
# Writing the Concrete Code

# 1 -------------------Bad

class Schedule
  def scheduled?(schedulable, start_date, end_date)
    puts "This #{schedulable.class} " +
          "is not scheduled\n" +
          " between #{start_date} and #{end_date}"
  end
end

class Bicycle
  attr_reader :schedule, :size, :chain, :tire_size

  # Inject the Schedule and provide a default
  def initialize(args={})
    @schedule = args[:schedule] || Schedule.new
    # ...
  end

  # Return true if this bicycle is available
  # during this (now Bicycle specific) interval.

  def schedulable?(start_date, end_date)
    !scheduled?(start_date - lead_days, end_date)
  end

  # Return the number of lead_days before a bicycle
  # can be scheduled.

  def lead_days
    1
  end

  # ...
end

require 'date'
starting = Date.parse('2015/09/04')
ending = Date.parse('2015/09/10')

b = Bicycle.new
b.schedulable?(starting, ending)

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
# Extracting the Abstraction

# 2 -------------------Good

module Schedulable
  attr_writer :schedule

  def schedule
    @schedule ||= ::Schedule.new
  end

  def schedulable?(start_date, end_date)
    !scheduled?(start_date - lead_days, end_date)
  end

  def scheduled?(start_date, end_date)
    schedule.scheduled?(self, start_date, end_date)
  end

  # includers may override
  def lead_days
    0
  end
end

class Bicycle
  include Schedulable

  def lead_days
    1
  end

  # ...
end

require 'date'
starting = Date.parse('2015/09/04')
ending = Date.parse('2015/09/10')

b = Bicycle.new
b.schedulable?(starting, ending)



class Vehicle
  include Schedulable

  def lead_days
    3
  end
  # ...
end

class Mechanic
  include Schedulable

  def lead_days
    4
  end

  # ...
end

v = Vehicle.new
v.schedulable?(starting, ending)
# This Vehicle is not scheduled
# between 2015-09-01 and 2015-09-10
# => true

m = Mechanic.new
m.schedulable?(starting, ending)
# This Mechanic is not scheduled
# between 2015-02-29 and 2015-09-10
# => true