DCI using EVIL.RB, Wroc_Love.rb 2013

dci_with_hacks.rb

# Firstly, install gems: 'evilr' and 'include'

# Example with User in a shop application.
# He has two roles
#   - buyer (with money on the account and so on)
#   - reviewer (he can review books he bought)


require 'evilr'
require 'include'

class User
  attr_reader :email
  
  def initialize(email)
    @email = email
    @money = 0
  end
end

class Buyer
  include User.to_module
  attr_reader :money
  
  # Yeah, these methods are kind of dumb, because we can 'buy' product for '-10', but it's implementation detail
  def buy(item_price)
    @money -= item_price
  end
  
  def add_money(amount)
    @money += amount
  end
end

class Reviewer < User
  include User.to_module
  
  def review(book_name)
    puts "#{book_name} was amazing!"
  end
end

example_session

# Example session in irb:
swistak35@raptop> irb
1.9.2p320 :001 > load 'dci_with_hacks.rb'
 => true 
1.9.2p320 :002 > x = Buyer.new("Swistak35")
 => #<Buyer:0x00000001505a18 @email="Swistak35", @money=0> 
1.9.2p320 :003 > x.money
 => 0 
1.9.2p320 :004 > x.add_money 10
 => 10 
1.9.2p320 :005 > x.money
 => 10 
1.9.2p320 :007 > x.class = Reviewer
 => Reviewer 
1.9.2p320 :008 > x.review "Ding dong"
Ding dong was amazing!
 => nil 
1.9.2p320 :009 > x.money
NoMethodError: undefined method `money' for #<Reviewer:0x00000001505a18>
        from (irb):9
        from /home/swistak35/.rvm/rubies/ruby-1.9.2-p320/bin/irb:16:in `<main>'
1.9.2p320 :010 > x.class = Buyer
 => Buyer 
1.9.2p320 :011 > x.money
 => 10