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Techtalk design patterns

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Techtalk design patterns

  1. 1. DESIGN PATTERNS Teeeechhh taaaaalkkkk
  2. 2. A design pattern is a general reusable solution to a commonly occurring problem within a given context in software design.A design pattern is not a finished design that can be transformed directly into source or machine code. It is a description or template for how to solve a problem that can be used in many different situations. The Gang of Four (GoF)
  3. 3. •Template Method •Strategy •Observer •Composite •Iterator •Command •Adapter •Proxy •Decorator •Singleton •Factory •Builder •Interpreter
  4. 4. • Template Method •Strategy •Observer •Composite •Iterator •Command •Adapter •Proxy •Decorator •Singleton •Factory •Builder •Interpreter
  5. 5. class Report! def initialize! @title = 'Monthly Report'! @text = ['Things are going', 'really, really well.']! end! ! def output_report(format)! if format == :plain! puts("*** #{@title} ***")! elsif format == :html! puts('<html>')! puts(' <head>')! puts(" <title>#{@title}</title>")! puts(' </head>')! puts(' <body>')! else! raise "Unknown format: #{format}"! end! ! @text.each do |line|! if format == :plain! puts(line)! else! puts(" <p>#{line}</p>" )! end! end! ! if format == :html! puts(' </body>')! puts('</html>')! end! end! end!
  6. 6. class Report! def initialize! @title = 'Monthly Report'! @text = ['Things are going', 'really, really well.']! end! ! def output_report! output_start! output_head! output_body_start! @text.each do |line|! output_line(line)! end! output_body_end! output_end! end! ! def output_start! end! ! def output_head! raise 'Called abstract method: output_head'! end! ! def output_body_start! end! ! def output_line(line)! raise 'Called abstract method: output_line'! end! ! def output_body_end! end! ! def output_end! end! end! Template method
  7. 7. class HTMLReport < Report! def output_start! puts('<html>')! end! ! def output_head! puts(' <head>')! puts(" <title>#{@title}</title>")! puts(' </head>')! end! ! def output_body_start! puts('<body>')! end! ! def output_line(line)! puts(" <p>#{line}</p>")! end! ! def output_body_end! puts('</body>')! end! ! def output_end! puts('</html>')! end! end!
  8. 8. •Template Method • Strategy •Observer •Composite •Iterator •Command •Adapter •Proxy •Decorator •Singleton •Factory •Builder •Interpreter
  9. 9. class Report! attr_reader :title, :text! attr_accessor :formatter! ! def initialize(formatter)! @title = 'Monthly Report'! @text = ['Things are going', 'really, really well.']! @formatter = formatter! end! ! def output_report! @formatter.output_report(self)! end! end! ! Report.new(HTMLFormatter.new)
  10. 10. class HTMLFormatter! def output_report(context)! puts('<html>')! puts(' <head>')! # Output The rest of the report ...! ! puts(" <title>#{context.title}</title>")! puts(' </head>')! puts(' <body>')! context.text.each do |line|! puts(" <p>#{line}</p>")! end! puts(' </body>')! ! puts('</html>')! end! end!
  11. 11. •Template Method •Strategy • Observer •Composite •Iterator •Command •Adapter •Proxy •Decorator •Singleton •Factory •Builder •Interpreter
  12. 12. class User! def save! save_to_database! if new_record?! notify_observers(:after_create)! end! notify_observers(:after_save)! end! end! ! class UserEmailObserver! def after_create(user)! UserMailer.welcome_email(user)! end! end! ! user = User.new! user.add_observer(UserEmailObserver.new)!
  13. 13. •Template Method •Strategy •Observer • Composite •Iterator •Command •Adapter •Proxy •Decorator •Singleton •Factory •Builder •Interpreter
  14. 14. class Task! attr_reader :name! ! def initialize(name)! @name = name! end! ! def get_time_required! 0.0! end! end
  15. 15. class CompositeTask < Task ! def initialize(name)! super(name)! @sub_tasks = []! end! ! def add_sub_task(task)! @sub_tasks << task! end! ! def remove_sub_task(task)! @sub_tasks.delete(task)! end! ! def get_time_required! time=0.0! @sub_tasks.each {|task| time += task.get_time_required}! time! end! end!
  16. 16. class MakeCakeTask < CompositeTask! def initialize! super('Make cake')! add_sub_task( MakeBatterTask.new )! add_sub_task( FillPanTask.new )! add_sub_task( BakeTask.new )! add_sub_task( FrostTask.new )! add_sub_task( LickSpoonTask.new )! end! end! ! MakeCakeTask.new.get_time_required
  17. 17. •Template Method •Strategy •Observer •Composite • Iterator •Command •Adapter •Proxy •Decorator •Singleton •Factory •Builder •Interpreter
  18. 18. External array = ['red', 'green', 'blue']! ! i = ArrayIterator.new(array)! while i.has_next?! puts "item: #{i.next_item}"! end! Hello Java ;-)
  19. 19. Internal array = ['red', 'green', 'blue']! array.each do |item|! puts "item: #{item}"! end!
  20. 20. External array1 = [1, 2]! array1 = [2, 3]! ! sum = 0! i1 = ArrayIterator.new(array1)! i2 = ArrayIterator.new(array2)! while i1.has_next? && i2.has_next?! sum += i1.next_item * i2.next_item! end!
  21. 21. •Template Method •Strategy •Observer •Composite •Iterator • Command •Adapter •Proxy •Decorator •Singleton •Factory •Builder •Interpreter
  22. 22. PrimerTemplate Method class SlickButton! def on_button_push! raise "Abstract method on_button_push"! end! end! ! class SaveButton < SlickButton! def on_button_push! document.save(filename)! end! end So many subclasses :-(
  23. 23. class SlickButton! attr_accessor :command! ! def initialize(command)! @command = command! end! ! def on_button_push! @command.execute if @command! end! end! ! class SaveCommand! def execute! # Save the current document...! end! end! Command Pattern
  24. 24. class SlickButton! attr_accessor :command! ! def initialize(&block)! @command = block! end! ! def on_button_push! @command.call if @command! end! end! ! save_button = SlickButton.new do! document.save(filename)! end! Lambda
  25. 25. Composite, Command PRIMER - INSTALLER
  26. 26. class Command! attr_reader :description! ! def initialize(description)! @description = description! end! ! def execute! end! ! def unexecute! end! end! ! class CreateFile < Command! def initialize(path, contents)! super "Create file: #{path}"! @path = path! @contents = contents! end! ! def execute! f = File.open(@path, "w")! f.write(@contents)! f.close! end! ! def unexecute! File.delete(@path)! end! end!
  27. 27. class CompositeCommand < Command! def initialize! @commands = []! end! ! def add_command(cmd)! @commands << cmd! end! ! def execute! @commands.each { |cmd| cmd.execute }! end! ! # ...! ! def unexecute! @commands.reverse.each { |cmd| cmd.unexecute }! end! ! # ...! ! def description! description = ''! @commands.each { |cmd| description += cmd.description + "n" }! return description! end! end!
  28. 28. class Installer < CompositeCommand! def initialize! add_command(CreateFile.new("file1.txt", "hello worldn"))! add_command(CopyFile.new("file1.txt", "file2.txt"))! add_command(DeleteFile.new("file1.txt"))! end! end! ! installer = Installer.new! installer.execute! puts installer.description!
  29. 29. •Template Method •Strategy •Observer •Composite •Iterator •Command • Adapter •Proxy •Decorator •Singleton •Factory •Builder •Interpreter
  30. 30. class Database! def initialize(adapter)! @adapter = adapter! end! ! def create_table(table_name, fields)! @adapter.create_table(table_name)! fields.each_pair do |name, type|! @adapter.create_column(table_name, name, type)! end! end! end! ! db = Database.new(MySQLAdapter.new(DB_URI))! db.create_table(:users, email: :string)!
  31. 31. •Template Method •Strategy •Observer •Composite •Iterator •Command •Adapter • Proxy •Decorator •Singleton •Factory •Builder •Interpreter
  32. 32. class AccountProtectionProxy! def initialize(real_account, owner_name)! @subject = real_account! @owner_name = owner_name! end! ! def withdraw(amount)! check_access! return @subject.withdraw(amount)! end! ! def check_access! if Etc.getlogin != @owner_name ! raise "Illegal access: #{Etc.getlogin} cannot access account."! end! end! end!
  33. 33. •Template Method •Strategy •Observer •Composite •Iterator •Command •Adapter •Proxy • Decorator •Singleton •Factory •Builder •Interpreter
  34. 34. class UserDecorator! attr_reader :user! delegate :first_name, :last_name,! :position, :institution, to: :user! ! def initialize(user)! @user = user! end! ! def short_name! "#{first_name[0]}. #{last_name}"! end! ! def description! "#{short_name} is a #{position} at #{institution}"! end! end! <p>! <b>Name:<b>! {{short_name}}! <br>! {{description}}! <p>!
  35. 35. •Template Method •Strategy •Observer •Composite •Iterator •Command •Adapter •Proxy •Decorator • Singleton •Factory •Builder •Interpreter
  36. 36. class SimpleLogger! @@instance = SimpleLogger.new! ! def self.instance! return @@instance! end! ! def warn(s)! puts s! end! end! ! SimpleLogger.instance.warn("I don't know what I'm doing")!
  37. 37. •Template Method •Strategy •Observer •Composite •Iterator •Command •Adapter •Proxy •Decorator •Singleton • Factory •Builder •Interpreter
  38. 38. factory :user do! first_name 'John'! last_name 'Doe'! admin false! ! factory :admin do! admin true! end! end! ! FactoryGirl.build(:user)! FactoryGirl.build(:admin)!
  39. 39. •Template Method •Strategy •Observer •Composite •Iterator •Command •Adapter •Proxy •Decorator •Singleton •Factory • Builder •Interpreter
  40. 40. user = UserBuilder.new('John', 'Doe')! .age(30)! .phone('1234567')! .address('Fake address 1234')! .build()! Hello Java ;-)
  41. 41. •Template Method •Strategy •Observer •Composite •Iterator •Command •Adapter •Proxy •Decorator •Singleton •Factory •Builder • Interpreter
  42. 42. AST (Abstract SyntaxTree) querying stuff, building SQL, etc. # Files that are bigger than 20KB and not writable,! # or are mp3 files! expr = Or.new(! And.new(Bigger.new(20.kilobytes), Not.new(Writable.new)),! FileName.new('*.mp3'))! expr.evaluate # => [File, File, ...]!
  43. 43. •teamleadi določite enega ki naj v naslednji 1 uri uporabi na projektu enega od patternov •checkmarks

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