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SOLID Ruby SOLID Rails

Michael Mahlberg
Michael Mahlberg

Here are a few ways the UsersController could be refactored to better follow the Interface Segregation Principle: 1. Extract authentication/authorization logic into a separate AuthenticationController concern. 2. Extract user profile/account management logic into an AccountsController. 3. Extract activation/registration logic into a separate RegistrationController. 4. Create separate interfaces/controllers for different user roles like AdminUsersController vs RegularUsersController. This avoids forcing all user-related actions onto a single controller, allowing each controller to focus on specific user workflows and responsibilities. Clients like regular users and admins would interact with specialized interfaces rather than depending on a monolithic UsersController.

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Michael Mahlberg, Consulting Guild AG Jens-Christian Fischer, InVisible GmbH SOLID Ruby - SOLID Rails Establishing a sustainable codebase 1
Who? Michael Mahlberg 2
Founder of roughly a dozen companies over the last two decades 3
>> relevance => nil 4
Working as A consultant on software processes, architecture & design for > 2 decades 5
>> relevance != nil => true 6
Who? Jens-Christian Fischer 7
Tinkerer, Practician, Author and generally interested in way too many things 8
What is SOLID? 9
SOLID is not a Law 10
PPP (by Robert C. Martin) Agile Software Development, Principles, Patterns, and Practices 11
Principles! You know - more like guidelines 12
SOLID SRP OCP LSP ISP DIP 13
S OL I D SRP OCP LSP ISP DIP 14
SRP Single Responsibility Principle A class should have one, and only one, reason to change. 15
require  'digest/sha1' class  User  <  ActiveRecord::Base    include  Authentication User Class    include  Authentication::ByPassword    include  Authentication::ByCookieToken    #TODO  Check  login  redirect  if  this  filter  is  skipped    #skip_after_filter  :store_location    #  Virtual  attribute  for  the  unencrypted  password    attr_accessor  :password    belongs_to  :country    has_one  :user_profile,  :dependent  =>  :destroy    has_one  :note            has_many  :queries    has_many  :tags,  :foreign_key  =>  "created_by"    has_many  :taggings,  :as  =>  :tagger    has_many  :organizations,  :through  =>  :affiliations    has_many  :affiliations    has_many  :locations,  :through  =>  :affiliations    has_many  :projects,  :through  =>  :memberships    has_many  :memberships    has_many  :public_assets,  :through  =>  :privileges    has_many  :descriptions,  :through  =>  :privileges    has_many  :assessments,  :through  =>  :privileges    has_many  :description_profiles,  :through  =>  :privileges    has_many  :privileges    has_many  :diaries    has_many  :roles,  :through  =>  :commitments    has_many  :commitments    has_many  :activities    has_many  :messages    has_many  :fellowships    has_many  :user_groups,  :through  =>  :fellowships    has_many  :survey_responses       16
So what‘s wrong with this? 17
From: user.rb class User < ActiveRecord::Base include Authentication include Authentication::ByPassword include Authentication::ByCookieToken ... belongs_to :country ... has_one :user_profile, :dependent => :destroy has_many :queries has_many :tags, :foreign_key => "created_by" ... validates_presence_of :login, :email, :country_id validates_presence_of :password, :if => :password_required? ... 18
From: user.rb acts_as_state_machine :initial => :pending state :pending, :enter => :make_activation_code state :active, :enter => :do_activate ... event :register do transitions :from => :passive, :to => :pending, :guard => Proc.new {|u| !(u.crypted_password.blank? && u.password.blank?) } end ... def message_threads self.message_threads + self.message_threads end 19
From: user.rb def forum_nickname self.user_profile.nickname.blank? ? "#{self.first_name} # {self.last_name}" : self.user_profile.nickname end def name "#{self.first_name} #{self.last_name}" rescue 'n/a' end def email_with_name "#{self.first_name} #{self.last_name} <#{self.email}>" end 20
From: user.rb def is_admin? self.roles.collect{|role| role.title}.include?('admin') end def countries [self.country] end 21
From: user.rb def boards Board.all :conditions => { :user_group_id => self.user_groups.collect{ |g| g.id }} end def discussions Discussion.all :conditions => { :board_id => self.boards.collect{ |b| b.id }} end def organization_roles role_ids = Affiliation.all(:conditions => {:user_id => self.id}).collect{|a| a.role_id}.uniq roles = Role.find(role_ids) end 22
From: user.rb def make_password_reset_code self.password_reset_code = Digest::SHA1.hexdigest ( Time.now.to_s.split(//).sort_by {rand}.join ) end def self.published_users User.all(:conditions => ['state = ?', 'published'], :order => 'login ASC', :include => [:user_profile]) end 23
Anyone notice a pattern? 24
Neither do we 25
Separation of Concerns 26
Authentication Roles Mailers State ... 27
So how? Mixins 28
New User Model class User < ActiveRecord::Base include Authentication include Authentication::ByPassword include Authentication::ByCookieToken include Project::UserStates include Project::UserMailer include Project::UserForum include Project::UserMessages ... end 29
UserMessages module Project module UserMessages # to be included in User Model has_many :messages def message_threads MessageThread.all(:conditions => ["sender_id = ? or receiver_id = ?", self.id, self.id]) end end end 30
Methods 31
def transfer(data, url) h = Net::HTTP.new(self.uri.host, self.uri.port) RAILS_DEFAULT_LOGGER.debug "connecting to CL: #{self.uri}" RAILS_DEFAULT_LOGGER.debug "connecting to CL: #{url}" resp = h.post(url, data, {'Content-Type' => 'application/xml'}) response_code = resp.code.to_i location = if response_code == 201 resp['Location'] else RAILS_DEFAULT_LOGGER.debug "error from CL: #{response_code}" RAILS_DEFAULT_LOGGER.debug "error from CL: #{resp.body}" @error = resp.body nil end [response_code, location] end 32
def transfer(data, document) if document.cl_document_url != nil self.uri = URI.parse(document.cl_document_url ) h = Net::HTTP.new(self.uri.host, self.uri.port) response = h.post(self.uri, data, {'Content-Type' => 'application/xml'}) else h = Net::HTTP.new(self.uri.host, self.uri.port) response = h.post("/tasks", data, {'Content-Type' => 'application/xml'}) end response_code = response.code.to_i if response_code == 201 location = response['Location'] document.cl_document_url = location document.save! else nil end [response_code, location] end 33
SRP Transfer def transfer data open_connection post data return location end def open_connection @http = Net::HTTP.new(self.uri.host, self.uri.port) end def post data @response = http.post(self.url, data, {'Content-Type' => 'application/xml'}) end 34
def location get_location if created? # returns nil if not created? end def response_code @response.code.to_i end def created? response_code == 201 end def get_location @response['Location'] end def error @response.body end 35
Add a 16-band equalizer & a BlueRay player to this... 36
And now to this... 37
S OL I D SRP OCP LSP ISP DIP 38
OCP Open Closed Principle You should be able to extend a classes behavior, without modifying it. 39
40
41
42
43
def makemove(map) From the Google x, y = map.my_position # calculate a move ... AI Challenge if(valid_moves.size == 0) map.make_move( :NORTH ) (Tronbot) else # choose move ... puts move # debug (like in the old days) map.make_move( move ) end end class Map ... def make_move(direction) $stdout << ({:NORTH=>1, :SOUTH=>3, :EAST=>2, :WEST=>4}[direction]) $stdout << "n" $stdout.flush end end 44
From the Google AI Challenge (Tronbot) def puts(*args) $stderr.puts *args end def p(*args) args.map!{|arg| arg.inspect} puts args end def print(*args) $stderr.print *args end 45
Design Sketch 46
class Outputter def initialize(io = $stderr) @io = io end def puts(*args) @io.puts *args end ... end out = Outputter.new out.puts "Testing" 47
S OL I D SRP OCP LSP ISP DIP 48
LSP Liskov Substitution Principle Derived classes must be substitutable for their base classes. 49
No Problem in Ruby Or so it seems... 50
No Interface... no problem? 51
Wrong ! 52
The classic violation 53
A square is a rectangle 54
Rectangle setX setY Square setX setY 55
Rectange >> class Rectangle >> attr_accessor :width, :height >> end => nil >> ?> shape = Rectangle.new => #<Rectangle:0x10114fad0> >> shape.width => nil >> shape.width=3 >> shape.width => 3 >> shape.height=5 >> shape.height => 5 >> shape.width => 3 56
Square >> class Square ?> def width >> @dimension ?> shape = Square.new >> end => #<Square:0x101107e88> ?> def height ?> puts shape.width >> @dimension nil >> end ?> shape.width=3 ?> def width= n => 3 >> @dimension = n ?> shape.width >> end => 3 ?> def height= n ?> shape.height >> @dimension = n => 3 >> end >> end 57
A Problem... >> s = [Rectangle.new, Square.new] => [#<Rectangle:0x1005642e8>, #<Square:0x100564298>] >> a_rectangle = s[rand(2)] => #<Square:0x100564298> >> a_rectangle.height=1 => 1 >> a_rectangle.width=3 => 3 Text >> a_rectangle.height => 3 58
CCD Common Conceptual Denominator 59
dup 60
irb 1:0> 5.respond_to? :dup => true irb 2:0> 5.dup TypeError: can't dup Fixnum from (irb):1:in `dup' from (irb):1 irb 3:0> http://blog.objectmentor.com/articles/2007/02/17/ liskov-substitution-principle-and-the-ruby-core-libraries 61
S OL I D SRP OCP LSP ISP DIP 62
ISP Interface Segregation Principle Make fine grained interfaces that are client specific. 63
64
Users Controller class UsersController < ApplicationController ssl_required :new, :create, :edit, :update, :destroy, :activate, :change_passwort, :forgot_password, :reset_password, :make_profile, :my_contacts ssl_allowed :eula, :index, :show access_control [:suspend, :unsuspend, :destroy, :purge, :delete, :admin, :ban, :remove_ban] => 'admin' before_filter :find_user skip_after_filter :store_location def show unless @user == current_user redirect_to access_denied_path(@locale) else respond_to do |format| format.html format.js { render :partial => "users/#{@context.title}/#{@partial}" } end end end ... 65
more UsersController def activate logout_keeping_session! user = User.find_by_activation_code(params[:activation_code]) unless params[:activation_code].blank? case when (!params[:activation_code].blank?) && user && !user.active? user.activate! flash[:notice] = t(:message_sign_up_complete) unless params[:context].blank? redirect_to login_path(:context => params[:context]) else redirect_to "/login" end when params[:activation_code].blank? flash[:error] = t(:message_activation_code_missing) redirect_back_or_default("/") else flash[:error] = t(:message_user_with_that_activation_code_missing) redirect_back_or_default("/") end end 66
User Class Revisited class User < ActiveRecord::Base ... end class Registration < ActiveRecord::Base set_table_name "users" acts_as_state_machine :initial => :pending state :pending, :enter => :make_activation_code state :active, :enter => :do_activate ... event :activate do transitions :from => :pending, :to => :active end ... end 67
class RegistrationController < ApplicationController ... def activate logout_keeping_session! code_is_blank = params[:activation_code].blank? registration = Registration.find_by_activation_code(params [:activation_code]) unless code_is_blank case when (!code_is_blank) && registration && !registratio.active? registration.activate! flash[:notice] = t(:message_sign_up_complete) unless params[:context].blank? redirect_to login_path(:context => params[:context]) else redirect_to "/login" end when code_is_blank flash[:error] = t(:message_activation_code_missing) redirect_back_or_default("/") else flash[:error] = t(:message_user_with_that_activation_code_missing) redirect_back_or_default("/") end end ... end 68
S OL I D SRP OCP LSP ISP DIP 69
DIP Dependency Inversion Principle Depend on abstractions, not on concretions. 70
71
From our OCP example to DIP out = Outputter.new out.puts "Testing" 72
The code we wish we had class TronBot def initialize @@out = TRON_ENVIRONMENT[:debugger] end def some_method ... @@out.puts "Testing" ... end end 73
TSTTCPW TRON_ENVIRONMENT = { :debugger => Outputter.new ($stderr), :game_engine => Outputter.new ($stdout), :user_io => Outputter.new ($stderr) } 74
Later... TRON_ENVIRONMENT = { :debugger => Outputter.new ($stderr), :game_engine => Outputter.new (TCP_OUTPUTTER), :user_io => Outputter.new ($stderr) } 75
DIP Violation in Controller format.js do render :update do |page| if @parent_object.class == EspGoal @esp_goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_esp_goal_descriptor", :locals => {:esp_goal_descriptor => @esp_goal_descriptor, :parent_object => @parent_object} else @goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_goal_descriptor", :locals => {:goal_descriptor => @goal_descriptor, :parent_object => @parent_object} end end end 76
DIP Violation in Controller format.js do render :update do |page| if @parent_object.class == EspGoal @esp_goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_esp_goal_descriptor", :locals => {:esp_goal_descriptor => @esp_goal_descriptor, :parent_object => @parent_object} else if @parent_object.class == Goal @goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_goal_descriptor", :locals => {:goal_descriptor => @goal_descriptor, :parent_object => @parent_object} else if @parent_object.class == LearningGoal ... ... end end end 77
78
1st Refactoring def show ... format.js do render :update do |page| page.replace_html "descriptor_#{@current_object.id}", @parent_object.page_replacement(@current_object) end end end class EspGoal def page_replacement child { :partial => "edit_esp_goal_descriptor", :locals => {:esp_goal_descriptor => child, :parent_object => self} } end end class Goal def page_replacement child { :partial => "edit_goal_descriptor", :locals => {:goal_descriptor => child, :parent_object => self} } end end 79
80
2nd Refactoring (wiring) class PartialContainer def add class_symbol, partial_replacement @@partinal_replacements.add( class_symbol => partial_replacement) end def self.partial_replacement an_object unless @@partial_replacments self.add( EspGoalReplacement.my_class_sym, EspGoalReplacment.new) self.add( GoalReplacement.my_class_sym, GoalReplacment.new) end @@partial_replacement[an_object.class] end end 81
class EspGoalReplacmenent 2nd Refactoring def self.my_class_sym end EspGoal.to_sym (Behaviour) def partial_definition child { :partial => "edit_esp_goal_descriptor", :locals => {:esp_goal_descriptor => child, :parent_object => child.esp_goal} } end end class GoalReplacmenent def self.my_class_sym Goal.to_sym end def partial_definition child { :partial => "edit_goal_descriptor", :locals => {:goal_descriptor => child, :parent_object => child.goal} } end end 82
DIP Violation in Controller format.js do render :update do |page| if @parent_object.class == EspGoal @esp_goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_esp_goal_descriptor", :locals => {:esp_goal_descriptor => @esp_goal_descriptor, :parent_object => @parent_object} else @goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_goal_descriptor", :locals => {:goal_descriptor => @goal_descriptor, :parent_object => @parent_object} end end end 83
2nd Refactoring - the Controller - def show ... format.js do render :update do |page| page.replace_html "descriptor_#{@current_object.id}", PartialContainer.partial_replacement(@parent_object). partial_definition(@current_object) end end end 84
85
SOLID SRP OCP LSP ISP DIP 86
SRP OCP LSP ISP DIP 87
Questions? S OL ID SRP OCP LSP ISP DIP 88
Vielen Dank! 89
Credits (1/2) PPP-Article (online) http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod Photos http://www.flickr.com/photos/dieterkarner/370967891/ http://www.flickr.com/photos/popcorncx/2221630487/sizes/l/ http://www.flickr.com/photos/bdesham/2432400623/ http://www.flickr.com/photos/popcorncx/2221630487/ http://www.flickr.com/photos/glennbatuyong/4081599002/in/photostream/ http://www.flickr.com/photos/glennbatuyong/4081599168/in/photostream/ http://www.flickr.com/photos/renfield/3865907619/ 90 90
Credits (2/2) Photos http://www.flickr.com/photos/renfield/3865907619/ http://www.flickr.com/photos/maxpower/5160699/ http://programmer.97things.oreilly.com/wiki/index.php/Uncle_Bob http://www.flickr.com/photos/georgivar/3288942086/ http://www.everystockphoto.com/photo.php?imageId=237523 http://www.flickr.com/photos/pasukaru76/3992935923/ 91 91
Lizense http://creativecommons.org/licenses/by-sa/ 3.0/de/ 92 92
Jens-Christian Fischer Michael Mahlberg InVisible GmbH Consulting Guild AG @jcfischer @MMahlberg jens-christian@invisible.ch mm@michaelmahlberg.de http://blog.invisible.ch http://agile-aspects.blogspot.com 93 93

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SOLID Ruby SOLID Rails

  • 1. Michael Mahlberg, Consulting Guild AG Jens-Christian Fischer, InVisible GmbH SOLID Ruby - SOLID Rails Establishing a sustainable codebase 1
  • 2. Who? Michael Mahlberg 2
  • 3. Founder of roughly a dozen companies over the last two decades 3
  • 5. Working as A consultant on software processes, architecture & design for > 2 decades 5
  • 6. >> relevance != nil => true 6
  • 7. Who? Jens-Christian Fischer 7
  • 8. Tinkerer, Practician, Author and generally interested in way too many things 8
  • 10. SOLID is not a Law 10
  • 11. PPP (by Robert C. Martin) Agile Software Development, Principles, Patterns, and Practices 11
  • 12. Principles! You know - more like guidelines 12
  • 13. SOLID SRP OCP LSP ISP DIP 13
  • 14. S OL I D SRP OCP LSP ISP DIP 14
  • 15. SRP Single Responsibility Principle A class should have one, and only one, reason to change. 15
  • 16. require  'digest/sha1' class  User  <  ActiveRecord::Base    include  Authentication User Class    include  Authentication::ByPassword    include  Authentication::ByCookieToken    #TODO  Check  login  redirect  if  this  filter  is  skipped    #skip_after_filter  :store_location    #  Virtual  attribute  for  the  unencrypted  password    attr_accessor  :password    belongs_to  :country    has_one  :user_profile,  :dependent  =>  :destroy    has_one  :note            has_many  :queries    has_many  :tags,  :foreign_key  =>  "created_by"    has_many  :taggings,  :as  =>  :tagger    has_many  :organizations,  :through  =>  :affiliations    has_many  :affiliations    has_many  :locations,  :through  =>  :affiliations    has_many  :projects,  :through  =>  :memberships    has_many  :memberships    has_many  :public_assets,  :through  =>  :privileges    has_many  :descriptions,  :through  =>  :privileges    has_many  :assessments,  :through  =>  :privileges    has_many  :description_profiles,  :through  =>  :privileges    has_many  :privileges    has_many  :diaries    has_many  :roles,  :through  =>  :commitments    has_many  :commitments    has_many  :activities    has_many  :messages    has_many  :fellowships    has_many  :user_groups,  :through  =>  :fellowships    has_many  :survey_responses       16
  • 17. So what‘s wrong with this? 17
  • 18. From: user.rb class User < ActiveRecord::Base include Authentication include Authentication::ByPassword include Authentication::ByCookieToken ... belongs_to :country ... has_one :user_profile, :dependent => :destroy has_many :queries has_many :tags, :foreign_key => "created_by" ... validates_presence_of :login, :email, :country_id validates_presence_of :password, :if => :password_required? ... 18
  • 19. From: user.rb acts_as_state_machine :initial => :pending state :pending, :enter => :make_activation_code state :active, :enter => :do_activate ... event :register do transitions :from => :passive, :to => :pending, :guard => Proc.new {|u| !(u.crypted_password.blank? && u.password.blank?) } end ... def message_threads self.message_threads + self.message_threads end 19
  • 20. From: user.rb def forum_nickname self.user_profile.nickname.blank? ? "#{self.first_name} # {self.last_name}" : self.user_profile.nickname end def name "#{self.first_name} #{self.last_name}" rescue 'n/a' end def email_with_name "#{self.first_name} #{self.last_name} <#{self.email}>" end 20
  • 21. From: user.rb def is_admin? self.roles.collect{|role| role.title}.include?('admin') end def countries [self.country] end 21
  • 22. From: user.rb def boards Board.all :conditions => { :user_group_id => self.user_groups.collect{ |g| g.id }} end def discussions Discussion.all :conditions => { :board_id => self.boards.collect{ |b| b.id }} end def organization_roles role_ids = Affiliation.all(:conditions => {:user_id => self.id}).collect{|a| a.role_id}.uniq roles = Role.find(role_ids) end 22
  • 23. From: user.rb def make_password_reset_code self.password_reset_code = Digest::SHA1.hexdigest ( Time.now.to_s.split(//).sort_by {rand}.join ) end def self.published_users User.all(:conditions => ['state = ?', 'published'], :order => 'login ASC', :include => [:user_profile]) end 23
  • 24. Anyone notice a pattern? 24
  • 27. Authentication Roles Mailers State ... 27
  • 28. So how? Mixins 28
  • 29. New User Model class User < ActiveRecord::Base include Authentication include Authentication::ByPassword include Authentication::ByCookieToken include Project::UserStates include Project::UserMailer include Project::UserForum include Project::UserMessages ... end 29
  • 30. UserMessages module Project module UserMessages # to be included in User Model has_many :messages def message_threads MessageThread.all(:conditions => ["sender_id = ? or receiver_id = ?", self.id, self.id]) end end end 30
  • 31. Methods 31
  • 32. def transfer(data, url) h = Net::HTTP.new(self.uri.host, self.uri.port) RAILS_DEFAULT_LOGGER.debug "connecting to CL: #{self.uri}" RAILS_DEFAULT_LOGGER.debug "connecting to CL: #{url}" resp = h.post(url, data, {'Content-Type' => 'application/xml'}) response_code = resp.code.to_i location = if response_code == 201 resp['Location'] else RAILS_DEFAULT_LOGGER.debug "error from CL: #{response_code}" RAILS_DEFAULT_LOGGER.debug "error from CL: #{resp.body}" @error = resp.body nil end [response_code, location] end 32
  • 33. def transfer(data, document) if document.cl_document_url != nil self.uri = URI.parse(document.cl_document_url ) h = Net::HTTP.new(self.uri.host, self.uri.port) response = h.post(self.uri, data, {'Content-Type' => 'application/xml'}) else h = Net::HTTP.new(self.uri.host, self.uri.port) response = h.post("/tasks", data, {'Content-Type' => 'application/xml'}) end response_code = response.code.to_i if response_code == 201 location = response['Location'] document.cl_document_url = location document.save! else nil end [response_code, location] end 33
  • 34. SRP Transfer def transfer data open_connection post data return location end def open_connection @http = Net::HTTP.new(self.uri.host, self.uri.port) end def post data @response = http.post(self.url, data, {'Content-Type' => 'application/xml'}) end 34
  • 35. def location get_location if created? # returns nil if not created? end def response_code @response.code.to_i end def created? response_code == 201 end def get_location @response['Location'] end def error @response.body end 35
  • 36. Add a 16-band equalizer & a BlueRay player to this... 36
  • 37. And now to this... 37
  • 38. S OL I D SRP OCP LSP ISP DIP 38
  • 39. OCP Open Closed Principle You should be able to extend a classes behavior, without modifying it. 39
  • 40. 40
  • 41. 41
  • 42. 42
  • 43. 43
  • 44. def makemove(map) From the Google x, y = map.my_position # calculate a move ... AI Challenge if(valid_moves.size == 0) map.make_move( :NORTH ) (Tronbot) else # choose move ... puts move # debug (like in the old days) map.make_move( move ) end end class Map ... def make_move(direction) $stdout << ({:NORTH=>1, :SOUTH=>3, :EAST=>2, :WEST=>4}[direction]) $stdout << "n" $stdout.flush end end 44
  • 45. From the Google AI Challenge (Tronbot) def puts(*args) $stderr.puts *args end def p(*args) args.map!{|arg| arg.inspect} puts args end def print(*args) $stderr.print *args end 45
  • 47. class Outputter def initialize(io = $stderr) @io = io end def puts(*args) @io.puts *args end ... end out = Outputter.new out.puts "Testing" 47
  • 48. S OL I D SRP OCP LSP ISP DIP 48
  • 49. LSP Liskov Substitution Principle Derived classes must be substitutable for their base classes. 49
  • 50. No Problem in Ruby Or so it seems... 50
  • 51. No Interface... no problem? 51
  • 52. Wrong ! 52
  • 54. A square is a rectangle 54
  • 55. Rectangle setX setY Square setX setY 55
  • 56. Rectange >> class Rectangle >> attr_accessor :width, :height >> end => nil >> ?> shape = Rectangle.new => #<Rectangle:0x10114fad0> >> shape.width => nil >> shape.width=3 >> shape.width => 3 >> shape.height=5 >> shape.height => 5 >> shape.width => 3 56
  • 57. Square >> class Square ?> def width >> @dimension ?> shape = Square.new >> end => #<Square:0x101107e88> ?> def height ?> puts shape.width >> @dimension nil >> end ?> shape.width=3 ?> def width= n => 3 >> @dimension = n ?> shape.width >> end => 3 ?> def height= n ?> shape.height >> @dimension = n => 3 >> end >> end 57
  • 58. A Problem... >> s = [Rectangle.new, Square.new] => [#<Rectangle:0x1005642e8>, #<Square:0x100564298>] >> a_rectangle = s[rand(2)] => #<Square:0x100564298> >> a_rectangle.height=1 => 1 >> a_rectangle.width=3 => 3 Text >> a_rectangle.height => 3 58
  • 59. CCD Common Conceptual Denominator 59
  • 60. dup 60
  • 61. irb 1:0> 5.respond_to? :dup => true irb 2:0> 5.dup TypeError: can't dup Fixnum from (irb):1:in `dup' from (irb):1 irb 3:0> http://blog.objectmentor.com/articles/2007/02/17/ liskov-substitution-principle-and-the-ruby-core-libraries 61
  • 62. S OL I D SRP OCP LSP ISP DIP 62
  • 63. ISP Interface Segregation Principle Make fine grained interfaces that are client specific. 63
  • 64. 64
  • 65. Users Controller class UsersController < ApplicationController ssl_required :new, :create, :edit, :update, :destroy, :activate, :change_passwort, :forgot_password, :reset_password, :make_profile, :my_contacts ssl_allowed :eula, :index, :show access_control [:suspend, :unsuspend, :destroy, :purge, :delete, :admin, :ban, :remove_ban] => 'admin' before_filter :find_user skip_after_filter :store_location def show unless @user == current_user redirect_to access_denied_path(@locale) else respond_to do |format| format.html format.js { render :partial => "users/#{@context.title}/#{@partial}" } end end end ... 65
  • 66. more UsersController def activate logout_keeping_session! user = User.find_by_activation_code(params[:activation_code]) unless params[:activation_code].blank? case when (!params[:activation_code].blank?) && user && !user.active? user.activate! flash[:notice] = t(:message_sign_up_complete) unless params[:context].blank? redirect_to login_path(:context => params[:context]) else redirect_to "/login" end when params[:activation_code].blank? flash[:error] = t(:message_activation_code_missing) redirect_back_or_default("/") else flash[:error] = t(:message_user_with_that_activation_code_missing) redirect_back_or_default("/") end end 66
  • 67. User Class Revisited class User < ActiveRecord::Base ... end class Registration < ActiveRecord::Base set_table_name "users" acts_as_state_machine :initial => :pending state :pending, :enter => :make_activation_code state :active, :enter => :do_activate ... event :activate do transitions :from => :pending, :to => :active end ... end 67
  • 68. class RegistrationController < ApplicationController ... def activate logout_keeping_session! code_is_blank = params[:activation_code].blank? registration = Registration.find_by_activation_code(params [:activation_code]) unless code_is_blank case when (!code_is_blank) && registration && !registratio.active? registration.activate! flash[:notice] = t(:message_sign_up_complete) unless params[:context].blank? redirect_to login_path(:context => params[:context]) else redirect_to "/login" end when code_is_blank flash[:error] = t(:message_activation_code_missing) redirect_back_or_default("/") else flash[:error] = t(:message_user_with_that_activation_code_missing) redirect_back_or_default("/") end end ... end 68
  • 69. S OL I D SRP OCP LSP ISP DIP 69
  • 70. DIP Dependency Inversion Principle Depend on abstractions, not on concretions. 70
  • 71. 71
  • 72. From our OCP example to DIP out = Outputter.new out.puts "Testing" 72
  • 73. The code we wish we had class TronBot def initialize @@out = TRON_ENVIRONMENT[:debugger] end def some_method ... @@out.puts "Testing" ... end end 73
  • 74. TSTTCPW TRON_ENVIRONMENT = { :debugger => Outputter.new ($stderr), :game_engine => Outputter.new ($stdout), :user_io => Outputter.new ($stderr) } 74
  • 75. Later... TRON_ENVIRONMENT = { :debugger => Outputter.new ($stderr), :game_engine => Outputter.new (TCP_OUTPUTTER), :user_io => Outputter.new ($stderr) } 75
  • 76. DIP Violation in Controller format.js do render :update do |page| if @parent_object.class == EspGoal @esp_goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_esp_goal_descriptor", :locals => {:esp_goal_descriptor => @esp_goal_descriptor, :parent_object => @parent_object} else @goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_goal_descriptor", :locals => {:goal_descriptor => @goal_descriptor, :parent_object => @parent_object} end end end 76
  • 77. DIP Violation in Controller format.js do render :update do |page| if @parent_object.class == EspGoal @esp_goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_esp_goal_descriptor", :locals => {:esp_goal_descriptor => @esp_goal_descriptor, :parent_object => @parent_object} else if @parent_object.class == Goal @goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_goal_descriptor", :locals => {:goal_descriptor => @goal_descriptor, :parent_object => @parent_object} else if @parent_object.class == LearningGoal ... ... end end end 77
  • 78. 78
  • 79. 1st Refactoring def show ... format.js do render :update do |page| page.replace_html "descriptor_#{@current_object.id}", @parent_object.page_replacement(@current_object) end end end class EspGoal def page_replacement child { :partial => "edit_esp_goal_descriptor", :locals => {:esp_goal_descriptor => child, :parent_object => self} } end end class Goal def page_replacement child { :partial => "edit_goal_descriptor", :locals => {:goal_descriptor => child, :parent_object => self} } end end 79
  • 80. 80
  • 81. 2nd Refactoring (wiring) class PartialContainer def add class_symbol, partial_replacement @@partinal_replacements.add( class_symbol => partial_replacement) end def self.partial_replacement an_object unless @@partial_replacments self.add( EspGoalReplacement.my_class_sym, EspGoalReplacment.new) self.add( GoalReplacement.my_class_sym, GoalReplacment.new) end @@partial_replacement[an_object.class] end end 81
  • 82. class EspGoalReplacmenent 2nd Refactoring def self.my_class_sym end EspGoal.to_sym (Behaviour) def partial_definition child { :partial => "edit_esp_goal_descriptor", :locals => {:esp_goal_descriptor => child, :parent_object => child.esp_goal} } end end class GoalReplacmenent def self.my_class_sym Goal.to_sym end def partial_definition child { :partial => "edit_goal_descriptor", :locals => {:goal_descriptor => child, :parent_object => child.goal} } end end 82
  • 83. DIP Violation in Controller format.js do render :update do |page| if @parent_object.class == EspGoal @esp_goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_esp_goal_descriptor", :locals => {:esp_goal_descriptor => @esp_goal_descriptor, :parent_object => @parent_object} else @goal_descriptor = @current_object page.replace_html "descriptor_#{@current_object.id}", :partial => "edit_goal_descriptor", :locals => {:goal_descriptor => @goal_descriptor, :parent_object => @parent_object} end end end 83
  • 84. 2nd Refactoring - the Controller - def show ... format.js do render :update do |page| page.replace_html "descriptor_#{@current_object.id}", PartialContainer.partial_replacement(@parent_object). partial_definition(@current_object) end end end 84
  • 85. 85
  • 86. SOLID SRP OCP LSP ISP DIP 86
  • 87. SRP OCP LSP ISP DIP 87
  • 88. Questions? S OL ID SRP OCP LSP ISP DIP 88
  • 93. Jens-Christian Fischer Michael Mahlberg InVisible GmbH Consulting Guild AG @jcfischer @MMahlberg [email protected] [email protected] http://blog.invisible.ch http://agile-aspects.blogspot.com 93 93