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Write Small Things (Code)

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Writing small code is hard. You know you should, but how do you actually do it? It's so much easier to write a large class. In this talk we'll build up a set of small classes starting from nothing …

Writing small code is hard. You know you should, but how do you actually do it? It's so much easier to write a large class. In this talk we'll build up a set of small classes starting from nothing using a set of directed refactorings applied as we build. All while keeping our classes small. We'll identify abstractions yearning to be free of their big object cages. In the process we'll also see how basic patterns such as composition, delegation and dependency injection emerge from using small objects. We'll even write some tests too.


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  • 1. Write Small Things Mark Menard @mark_menard Enable Labs Los Angeles Ruby Conf 2014 @mark_menard Enable Labs 1 WiteSmallThings - February 8, 2014
  • 2. Who is Mark Menard Husband of Sylva! Father of Ezra and Avi! From and Resides inTroy, NY! Owner of Enable Labs a boutique consultancy doing Web and Mobile Development! Has done for about five years! Doing software development for a long time @mark_menard Enable Labs 2 WiteSmallThings - February 8, 2014
  • 3. ‘The great thing about writing shitty code that “just works,” is that it is too risky and too expensive to change, so it lives forever.’! -Reginald Braithwaite @raganwald @mark_menard Enable Labs 3 WiteSmallThings - February 8, 2014
  • 4. Introduction @mark_menard Enable Labs 4 WiteSmallThings - February 8, 2014
  • 5. What is meant by small? @mark_menard Enable Labs 5 WiteSmallThings - February 8, 2014
  • 6. It’s not about total line count. @mark_menard Enable Labs 6 WiteSmallThings - February 8, 2014
  • 7. It’s not about method count. @mark_menard Enable Labs 7 WiteSmallThings - February 8, 2014
  • 8. It’s not about class count. @mark_menard Enable Labs 8 WiteSmallThings - February 8, 2014
  • 9. So, what do I mean by small things? Small methods! Small classes @mark_menard Enable Labs 9 WiteSmallThings - February 8, 2014
  • 10. Why should we strive for small code? • • • • We don’t know what the future will bring! Raise the level of abstraction! Create composable components! Prefer delegation over inheritance Enable Future Change @mark_menard Enable Labs 10 WiteSmallThings - February 8, 2014
  • 11. What are the challenges of small code? • • Dependency Management! Context Management @mark_menard Enable Labs 11 WiteSmallThings - February 8, 2014
  • 12. The goal: Small units of understandable code that are amenable to change. @mark_menard Enable Labs 12 WiteSmallThings - February 8, 2014
  • 13. Our Three Main Tools • • • Extract Method! Extract Class! Composed Method @mark_menard Enable Labs 13 WiteSmallThings - February 8, 2014
  • 14. Methods @mark_menard Enable Labs 14 WiteSmallThings - February 8, 2014
  • 15. “The object programs that live best and longest are those with short methods.”! ! ! ! ! ! ! -Refactoring by Fields, Harvey, Fowler, Black @mark_menard Enable Labs 15 WiteSmallThings - February 8, 2014
  • 16. The first rule of methods: @mark_menard Enable Labs 16 WiteSmallThings - February 8, 2014
  • 17. Do one thing. Do it well. Do only that thing. @mark_menard Enable Labs 17 WiteSmallThings - February 8, 2014
  • 18. Use Descriptive Names @mark_menard Enable Labs 18 WiteSmallThings - February 8, 2014
  • 19. The fewer arguments the better. @mark_menard Enable Labs 19 WiteSmallThings - February 8, 2014
  • 20. Separate Queries from Commands @mark_menard Enable Labs 20 WiteSmallThings - February 8, 2014
  • 21. Don’t Repeat Yourself @mark_menard Enable Labs 21 WiteSmallThings - February 8, 2014
  • 22. Let’s Build a Command Line Option Library @mark_menard Enable Labs 22 WiteSmallThings - February 8, 2014
  • 23. options = CommandLineOptions.new(ARGV) do option :c option :v option :e end ! if options.has(:c) # Do something end ! if options.has(:v) # Do something else end ! if options.has(:e) # Do the other thing end Enable Labs !23 23 @mark_menard WiteSmallThings - February 8, 2014
  • 24. describe CommandLineOptions do ! describe 'options' do ! let(:parser) { CommandLineOptions.new { option :c } } ! it "are true if present" do … ! it "are false if absent" do … end end Enable Labs !24 24 @mark_menard WiteSmallThings - February 8, 2014
  • 25. CommandLineOptions options are true if present are false if absent ! Finished in 0.00206 seconds 2 examples, 2 failures Enable Labs !25 25 @mark_menard WiteSmallThings - February 8, 2014
  • 26. class CommandLineOptions ! attr_accessor :argv attr_reader :options ! def initialize (argv = [], &block) @options = [] @argv = argv instance_eval &block end ! def has (option_flag) options.include?(option_flag) && argv.include?("-#{option_flag}") end ! options = CommandLineOptions.new(ARGV) do def option (option_flag) option :c options << option_flag option :v end option :e ! end end Enable Labs !26 26 @mark_menard WiteSmallThings - February 8, 2014
  • 27. CommandLineOptions options are true if present are false if absent ! Finished in 0.00206 seconds 2 examples, 0 failures Enable Labs !27 27 @mark_menard WiteSmallThings - February 8, 2014
  • 28. Done! @mark_menard Enable Labs 28 WiteSmallThings - February 8, 2014
  • 29. # some_ruby_program -v -efoo ! options = CommandLineOptions.new(ARGV) do option :v option :e, :string end ! if options.has(:v) # Do something end ! if options.has(:e) some_value = options.value(:e) # Do something with the expression end Enable Labs !29 29 @mark_menard WiteSmallThings - February 8, 2014
  • 30. describe CommandLineOptions do ! describe "boolean options" do let(:options) { CommandLineOptions.new { option :c } } it "are true if present" do … it "are false if absent" do … end ! describe "string options" do let(:options) { CommandLineOptions.new { option :e, :string } } it "must have content" do … it "can return the value" do … it "return nil if not in argv" do … end end Enable Labs !30 30 @mark_menard WiteSmallThings - February 8, 2014
  • 31. CommandLineOptions boolean options are true if present are false if absent string options must have content (FAILED - 1) can return the value (FAILED - 2) return nil if not in argv (FAILED - 3) ! Failures: ! ! ! ! 1) CommandLineOptions string options must have content Failure/Error: expect(options.valid?).to be_false NoMethodError: undefined method `valid?' for #<CommandLineOptions:0x00000102cc8fa0> # ./spec/command_line_options_spec.rb:26:in `block (3 levels) in <top (required)>' 2) CommandLineOptions string options can return the value Failure/Error: expect(options.value(:e)).to eq("foo") NoMethodError: undefined method `value' for #<CommandLineOptions:0x00000102cca1c0> # ./spec/command_line_options_spec.rb:31:in `block (3 levels) in <top (required)>' 3) CommandLineOptions string options return nil if not in argv Failure/Error: expect(options.value(:e)).to be_nil NoMethodError: undefined method `value' for #<CommandLineOptions:0x00000102cc2a38> # ./spec/command_line_options_spec.rb:35:in `block (3 levels) in <top (required)>' Finished in 0.00205 seconds 5 examples, 3 failures Enable Labs !31 31 @mark_menard WiteSmallThings - February 8, 2014
  • 32. def valid? options.each do |option_flag, option_type| raw_option_value = argv.find { |arg| arg =~ /-#{option_flag}/ } return false if raw_option_value.length < 3 && option_type == :string end end Enable Labs !32 32 @mark_menard WiteSmallThings - February 8, 2014
  • 33. CommandLineOptions boolean options are true if present are false if absent string options must have content can return the value (FAILED - 1) return nil if not in argv (FAILED - 2) ! Failures: ! 1) CommandLineOptions string options can return the value Failure/Error: expect(options.value(:e)).to eq("foo") NoMethodError: undefined method `value' for #<CommandLineOptions:0x00000101cbb6f8> # ./spec/command_line_options_spec.rb:31:in `block (3 levels) in <top (required)>' ! 2) CommandLineOptions string options return nil if not in argv Failure/Error: expect(options.value(:e)).to be_nil NoMethodError: undefined method `value' for #<CommandLineOptions:0x00000101cba2a8> # ./spec/command_line_options_spec.rb:35:in `block (3 levels) in <top (required)>' ! Finished in 0.00206 seconds 5 examples, 2 failures Enable Labs !33 33 @mark_menard WiteSmallThings - February 8, 2014
  • 34. def value (option_flag) raw_option_value = argv.find { |arg| arg =~ /-#{option_flag}/ } return nil unless raw_option_value option_type = options[option_flag] return raw_option_value[2..-1] if option_type == :string end Enable Labs !34 34 @mark_menard WiteSmallThings - February 8, 2014
  • 35. CommandLineOptions boolean options are true if present are false if absent string options must have content can return the value return nil if not in argv ! Finished in 0.00236 seconds 5 examples, 0 failures Enable Labs !35 35 @mark_menard WiteSmallThings - February 8, 2014
  • 36. def valid? options.each do |option_flag, option_type| raw_option_value = argv.find { |arg| arg =~ /-#{option_flag}/ } return false if raw_option_value.length < 3 && option_type == :string end end ! def value (option_flag) raw_option_value = argv.find { |arg| arg =~ /-#{option_flag}/ } return nil unless raw_option_value option_type = options[option_flag] return raw_option_value[2..-1] if option_type == :string end Enable Labs !36 36 @mark_menard WiteSmallThings - February 8, 2014
  • 37. Extract Method Refactoring def print_invoice_for_amount (amount) print_header puts "Name: #{@name}" puts "Amount: #{amount}" end Same level of abstraction def print_invoice_for_amount (amount) print_header print_details (amount) end ! def print_details (amount) puts "Name: #{@name}" puts "Amount: #{amount}" end Move this to here High level of abstraction Low level of abstraction @mark_menard Enable Labs 37 WiteSmallThings - February 8, 2014
  • 38. ! ! def valid? options.each do |option_flag, option_type| return false if option_type == :string && raw_value_for_option(option_flag).length < 3 end end def value (option_flag) raw_option_value = raw_value_for_option(option_flag) return nil unless raw_option_value option_type = options[option_flag] return raw_option_value[2..-1] if option_type == :string end private def raw_value_for_option (option_flag) argv.find { |arg| arg =~ /-#{option_flag}/ } end Enable Labs !38 38 @mark_menard WiteSmallThings - February 8, 2014
  • 39. CommandLineOptions boolean options are true if present are false if absent string options must have content can return the value return nil if not in argv ! Finished in 0.00236 seconds 5 examples, 0 failures Enable Labs !39 39 @mark_menard WiteSmallThings - February 8, 2014
  • 40. class CommandLineOptions ! ! ! ! ! ! ! attr_accessor :argv attr_reader :options def initialize (argv = [], &block) @options = {} @argv = argv instance_eval &block end def has (option_flag) options.include?(option_flag) && argv.include?("-#{option_flag}") end def option (option_flag, option_type = :boolean) options[option_flag] = option_type end def valid? options.each do |option_flag, option_type| return false if option_type == :string && raw_value_for_option(option_flag).length < 3 end end def value (option_flag) raw_option_value = raw_value_for_option(option_flag) return nil unless raw_option_value option_type = options[option_flag] return raw_option_value[2..-1] if option_type == :string end private def raw_value_for_option (option_flag) argv.find { |arg| arg =~ /-#{option_flag}/ } end end Enable Labs !40 40 @mark_menard WiteSmallThings - February 8, 2014
  • 41. ! ! def valid? options.each do |option_flag, option_type| return false if option_type == :string && raw_value_for_option(option_flag).length < 3 end end def value (option_flag) raw_option_value = raw_value_for_option(option_flag) return nil unless raw_option_value option_type = options[option_flag] return raw_option_value[2..-1] if option_type == :string end private def raw_value_for_option (option_flag) argv.find { |arg| arg =~ /-#{option_flag}/ } end Enable Labs !41 41 @mark_menard WiteSmallThings - February 8, 2014
  • 42. Done! @mark_menard Enable Labs 42 WiteSmallThings - February 8, 2014
  • 43. # some_ruby_program -v -efoo -i100 ! options = CommandLineOptions.new(ARGV) do option :v option :e, :string option :i, :integer end ! verbose = options.value(:v) expression = options.value(:e) iteration_count = options.value(:i) || 1 Enable Labs !43 43 @mark_menard WiteSmallThings - February 8, 2014
  • 44. describe "integer options" do it "must have content" it "must be an integer" it "can return the value as an integer" it "returns nil if not in argv" end Enable Labs !44 44 @mark_menard WiteSmallThings - February 8, 2014
  • 45. CommandLineOptions boolean options are true if present are false if absent string options must have content can return the value return nil if not in argv integer options must have content (PENDING: No reason given) must be an integer (PENDING: Not yet implemented) can return the value as an integer (PENDING: Not yet implemented) returns nil if not in argv (PENDING: Not yet implemented) Enable Labs !45 45 @mark_menard WiteSmallThings - February 8, 2014
  • 46. let(:options) { CommandLineOptions.new { option :i, :integer } } ! it "must have content" do options.argv = [ "-i" ] expect(options.valid?).to be_false end Enable Labs !46 46 @mark_menard WiteSmallThings - February 8, 2014
  • 47. def valid? options.each do |option_flag, option_type| return false if option_type == :string && raw_value_for_option(option_flag).length < 3 end end Enable Labs !47 47 @mark_menard WiteSmallThings - February 8, 2014
  • 48. def valid? options.each do |option_flag, option_type| return false if (option_type == :string || option_type == :integer)&& raw_value_for_option(option_flag).length < 3 end end Enable Labs !48 48 @mark_menard WiteSmallThings - February 8, 2014
  • 49. it "must be an integer" do options.argv = [ "-inot_an_integer" ] expect(options.valid?).to be_false end Enable Labs !49 49 @mark_menard WiteSmallThings - February 8, 2014
  • 50. def valid? options.each do |option_flag, option_type| return false if (option_type == :string || option_type == :integer) && raw_value_for_option(option_flag).length < 3 return false unless option_type == :integer && (Integer(raw_value_for_option(option_flag)[2..-1]) rescue false) end end Enable Labs !50 50 @mark_menard WiteSmallThings - February 8, 2014
  • 51. CommandLineOptions boolean options are true if present are false if absent string options must have content can return the value return nil if not in argv integer options must have content must be an integer can return the value as an integer (PENDING: Not yet implemented) returns nil if not in argv (PENDING: Not yet implemented) Enable Labs !51 51 @mark_menard WiteSmallThings - February 8, 2014
  • 52. class CommandLineOptions ! ! ! ! ! ! ! ! attr_accessor :argv attr_reader :options def initialize (argv = [], &block) @options = {} @argv = argv instance_eval &block end def has (option_flag) options.include?(option_flag) && argv.include?("-#{option_flag}") end def option (option_flag, option_type = :boolean) options[option_flag] = option_type end def valid? options.each do |option_flag, option_type| return false if (option_type == :string || option_type == :integer) && raw_value_for_option(option_flag).length < 3 return false unless option_type == :integer && (Integer(raw_value_for_option(option_flag)[2..-1]) rescue false) end end def value (option_flag) raw_option_value = raw_value_for_option(option_flag) return nil unless raw_option_value option_type = options[option_flag] return raw_option_value[2..-1] if option_type == :string end private def raw_value_for_option (option_flag) argv.find { |arg| arg =~ /-#{option_flag}/ } end end Enable Labs !52 52 @mark_menard WiteSmallThings - February 8, 2014
  • 53. def valid? options.each do |option_flag, option_type| return false if (option_type == :string || option_type == :integer) && raw_value_for_option(option_flag).length < 3 return false unless option_type == :integer && (Integer(raw_value_for_option(option_flag)[2..-1]) rescue false) end end Enable Labs !54 54 @mark_menard WiteSmallThings - February 8, 2014
  • 54. Integer("foo") rescue false #=> false "foo".to_i #=> 0 !!!!!!! Enable Labs !55 55 @mark_menard WiteSmallThings - February 8, 2014
  • 55. ! def valid? options.each do |option_flag, option_type| case(option_type) when :string return false if raw_value_for_option(option_flag).length < 3 when :integer return false if raw_value_for_option(option_flag).length < 3 return false unless (Integer(raw_value_for_option(option_flag)[2..-1]) rescue false) end end end Enable Labs !56 56 @mark_menard WiteSmallThings - February 8, 2014
  • 56. def valid? options.each do |option_flag, option_type| case(option_type) when :string return false if raw_value_for_option(option_flag).length < 3 when :integer return false if raw_value_for_option(option_flag).length < 3 return false unless (Integer(raw_value_for_option(option_flag)[2..-1]) rescue false) when :boolean end end end Enable Labs !57 57 @mark_menard WiteSmallThings - February 8, 2014
  • 57. CommandLineOptions boolean options are true if present are false if absent string options must have content can return the value return nil if not in argv integer options must have content must be an integer can return the value as an integer (PENDING: Not yet implemented) returns nil if not in argv (PENDING: Not yet implemented) Enable Labs !58 58 @mark_menard WiteSmallThings - February 8, 2014
  • 58. def valid? options.each do |option_flag, option_type| case(option_type) when :string return false unless string_option_valid?(raw_value_for_option(option_flag)) when :integer return false unless integer_option_valid?(raw_value_for_option(option_flag)) when :boolean end end end ! private def string_option_valid? (raw_value) extract_value_from_raw_value(raw_value).length > 0 end ! private def integer_option_valid? (raw_value) extract_value_from_raw_value(raw_value).length > 0 && (Integer(extract_value_from_raw_value(raw_value)) rescue false) end Enable Labs !59 59 @mark_menard WiteSmallThings - February 8, 2014
  • 59. private def boolean_option_valid? (raw_value) true end Enable Labs !60 60 @mark_menard WiteSmallThings - February 8, 2014
  • 60. CommandLineOptions boolean options are true if present are false if absent string options must have content can return the value return nil if not in argv integer options must have content must be an integer can return the value as an integer (PENDING: Not yet implemented) returns nil if not in argv (PENDING: Not yet implemented) Enable Labs !61 61 @mark_menard WiteSmallThings - February 8, 2014
  • 61. def valid? options.each do |option_flag, option_type| return false unless send("#{option_type}_option_valid?", raw_value_for_option(option_flag)) end end Enable Labs !62 62 @mark_menard WiteSmallThings - February 8, 2014
  • 62. def valid? options.each do |option_flag, option_type| return false unless option_valid?(option_type, raw_value_for_option(option_flag)) end end ! private def option_valid? (option_type, raw_value) send("#{option_type}_option_valid?", raw_value) end Enable Labs !63 63 @mark_menard WiteSmallThings - February 8, 2014
  • 63. CommandLineOptions boolean options are true if present are false if absent string options must have content is valid when there is content can return the value return nil if not in argv integer options must have content must be an integer can return the value as an integer returns nil if not in argv (PENDING: Not yet implemented) ! Pending: CommandLineOptions integer options returns nil if not in argv # Not yet implemented # ./spec/command_line_options_spec.rb:61 ! Finished in 0.00291 seconds 10 examples, 0 failures, 1 pending Enable Labs !64 64 @mark_menard WiteSmallThings - February 8, 2014
  • 64. ! ! class CommandLineOptions ! ! ! ! ! ! ! ! ! ! ! attr_accessor :argv attr_reader :options def initialize (argv = [], &block) @options = {} @argv = argv instance_eval &block end def has (option_flag) options.include?(option_flag) && argv.include?("-#{option_flag}") end def valid? options.each do |option_flag, option_type| return false unless option_valid?(option_type, raw_value_for_option(option_flag)) end end def value (option_flag) raw_option_value = raw_value_for_option(option_flag) return nil unless raw_option_value option_type = options[option_flag] return extract_value_from_raw_value(raw_option_value) if option_type == :string end private def option (option_flag, option_type = :boolean) options[option_flag] = option_type end private def option_valid? (option_type, raw_value) send("#{option_type}_option_valid?", raw_value) end private def string_option_valid? (raw_value) extract_value_from_raw_value(raw_value).length > 0 end private def integer_option_valid? (raw_value) extract_value_from_raw_value(raw_value).length > 0 && (Integer(extract_value_from_raw_value(raw_value)) rescue false) end private def boolean_option_valid? (raw_value) true end private def extract_value_from_raw_value (raw_value) raw_value[2..-1] end private def raw_value_for_option (option_flag) argv.find { |arg| arg =~ /-#{option_flag}/ } end end Enable Labs !65 65 @mark_menard WiteSmallThings - February 8, 2014
  • 65. def has (option_flag) options.include?(option_flag) && argv.include?("-#{option_flag}") end ! def valid? options.each do |option_flag, option_type| return false unless option_valid?(option_type, raw_value_for_option(option_flag)) end end ! def value (option_flag) raw_option_value = raw_value_for_option(option_flag) return nil unless raw_option_value option_type = options[option_flag] return extract_value_from_raw_value(raw_option_value) if option_type == :string end Enable Labs !66 66 @mark_menard WiteSmallThings - February 8, 2014
  • 66. Classes @mark_menard Enable Labs 67 WiteSmallThings - February 8, 2014
  • 67. How do we write small classes? • • • • • • • Write small methods! Talk to the class! Find a good name! Isolate Responsibilities! Find cohesive sets of variables/properties! Extract Class! Move method @mark_menard Enable Labs 68 WiteSmallThings - February 8, 2014
  • 68. What are the characteristics of a well designed small class? • • • • • • Single responsibility! Cohesive properties! Small public interface (preferably a handful of methods at the most)! Implements a single Use Case if possible! Primary logic is expressed in a composed method! Dependencies are injected @mark_menard Enable Labs 69 WiteSmallThings - February 8, 2014
  • 69. describe StringOption do let(:string_option) { StringOption.new('s', '-sfoo') } ! it it it it end "has a flag" "is valid when it has a value" "can return it's value when present" "returns nil if the flag has no raw value" Enable Labs !70 70 @mark_menard WiteSmallThings - February 8, 2014
  • 70. CommandLineOptions boolean options are true if present are false if absent string options must have content is valid when there is content can return the value return nil if not in argv integer options must have content must be an integer can return the value as an integer returns nil if not in argv (PENDING: Not yet implemented) ! StringOption has a flag (PENDING: No reason given) is valid when it has a value (PENDING: Not yet implemented) can return it's value when present (PENDING: Not yet implemented) returns nil if the flag has no raw value (PENDING: Not yet implemented) Enable Labs !71 71 @mark_menard WiteSmallThings - February 8, 2014
  • 71. class StringOption ! attr_reader :flag ! def initialize (flag, raw_value) @flag = flag @raw_value = raw_value end ! end Enable Labs !72 72 @mark_menard WiteSmallThings - February 8, 2014
  • 72. it "is valid when it has a value" do expect(string_option.valid?).to be_true end Enable Labs !73 73 @mark_menard WiteSmallThings - February 8, 2014
  • 73. class StringOption class CommandLineOptions ! ! ! private def string_option_valid? (raw_value) extract_value_from_raw_value(raw_value).length > 0 end ! end ! ! ! attr_reader :flag, :raw_value def initialize (flag, raw_value) @flag = flag @raw_value = raw_value end def valid? extract_value_from_raw_value.length > 0 end private def extract_value_from_raw_value raw_value[2..-1] end end Enable Labs !74 74 @mark_menard WiteSmallThings - February 8, 2014
  • 74. class StringOption ! attr_reader :flag, :raw_value ! def initialize (flag, raw_value) @flag = flag @raw_value = raw_value end ! def valid? extract_value_from_raw_value.length > 0 end ! private def extract_value_from_raw_value raw_value[2..-1] end ! end Enable Labs !75 75 @mark_menard WiteSmallThings - February 8, 2014
  • 75. private def string_option_valid? (raw_value) StringOption.new("", raw_value).valid? end Enable Labs !76 76 @mark_menard WiteSmallThings - February 8, 2014
  • 76. class IntegerOption ! attr_reader :flag, :raw_value ! def initialize (flag, raw_value) @flag = flag @raw_value = raw_value end ! def valid? extract_value_from_raw_value.length > 0 && real_value_is_integer? end ! private def extract_value_from_raw_value raw_value[2..-1] end ! private def real_value_is_integer? (Integer(extract_value_from_raw_value) rescue false) end ! end Enable Labs !77 77 @mark_menard WiteSmallThings - February 8, 2014
  • 77. class StringOption ! attr_reader :flag, :raw_value ! def initialize (flag, raw_value) @flag = flag @raw_value = raw_value end ! def valid? extract_value_from_raw_value.length > 0 end ! private def extract_value_from_raw_value raw_value[2..-1] end ! end Enable Labs !78 78 @mark_menard WiteSmallThings - February 8, 2014
  • 78. class OptionWithContent ! attr_reader :flag, :raw_value ! def initialize (flag, raw_value) @flag = flag @raw_value = raw_value end ! def valid? extract_value_from_raw_value.length > 0 end ! private def extract_value_from_raw_value raw_value[2..-1] end ! end Enable Labs !79 79 @mark_menard WiteSmallThings - February 8, 2014
  • 79. class StringOption < OptionWithContent end ! class IntegerOption < OptionWithContent ! def valid? super && real_value_is_integer? end ! private def real_value_is_integer? (Integer(extract_value_from_raw_value) rescue false) end ! end Enable Labs !80 80 @mark_menard WiteSmallThings - February 8, 2014
  • 80. CommandLineOptions boolean options are true if present are false if absent string options must have content is valid when there is content can return the value return nil if not in argv integer options must have content must be an integer can return the value as an integer returns nil if not in argv (PENDING: Not yet implemented) ! StringOption has a flag is valid when it has a value can return it's value when present (PENDING: Not yet implemented) returns nil if the flag has no raw value (PENDING: Not yet implemented) Enable Labs !81 81 @mark_menard WiteSmallThings - February 8, 2014
  • 81. Dependencies @mark_menard Enable Labs 83 WiteSmallThings - February 8, 2014
  • 82. How do we deal with Dependencies? • • Dependency Injection! Depend on Abstractions @mark_menard Enable Labs 82 WiteSmallThings - February 8, 2014
  • 83. private def option (option_flag, option_type = :boolean) options[option_flag] = option_type end private def option (option_flag, option_type = :boolean) options[option_flag] = case (option_type) when :boolean return BooleanOption.new(option_flag, nil) when :string return StringOption.new(option_flag, nil) when :integer return IntegerOption.new(option_flag, nil) end end private def option (option_flag, option_type = :boolean) option_class = "#{option_type}_option".camelize.constantize options[option_flag] = option_class.new(option_flag, nil) end Enable Labs !84 84 @mark_menard WiteSmallThings - February 8, 2014
  • 84. How do we isolate abstractions? Separate the “what” from the “how”. @mark_menard Enable Labs 85 WiteSmallThings - February 8, 2014
  • 85. CommandLineOptions boolean options are true if present are false if absent string options must have content (FAILED - 1) is valid when there is content (FAILED - 2) can return the value (FAILED - 3) return nil if not in argv integer options must have content (FAILED - 4) must be an integer (FAILED - 5) can return the value as an integer returns nil if not in argv (PENDING: Not yet implemented) ! StringOption has a flag is valid when it has a value can return it's value when present (PENDING: Not yet implemented) returns nil if the flag has no raw value (PENDING: Not yet implemented) Enable Labs !86 86 @mark_menard WiteSmallThings - February 8, 2014
  • 86. def valid? options.each do |option_flag, option_type| return false unless option_valid?(option_type, raw_value_for_option(option_flag)) end end def valid? options.values.all?(&:valid?) end Enable Labs !87 87 @mark_menard WiteSmallThings - February 8, 2014
  • 87. CommandLineOptions boolean options are true if present are false if absent string options must have content is valid when there is content can return the value (FAILED - 1) return nil if not in argv integer options must have content must be an integer can return the value as an integer returns nil if not in argv (PENDING: Not yet implemented) ! StringOption has a flag is valid when it has a value can return it's value when present (PENDING: Not yet implemented) returns nil if the flag has no raw value (PENDING: Not yet implemented) Enable Labs !88 88 @mark_menard WiteSmallThings - February 8, 2014
  • 88. def value (option_flag) raw_option_value = argv.find { |arg| arg =~ /-#{option_flag}/ } return nil unless raw_option_value option_type = options[option_flag] return raw_option_value[2..-1] if option_type == :string end def value (option_flag) options[option_flag].value end Enable Labs !89 89 @mark_menard WiteSmallThings - February 8, 2014
  • 89. 1) CommandLineOptions string options can return the value Failure/Error: expect(options.value(:e)).to eq("foo") NoMethodError: undefined method `value' for #<StringOption:0x00000101b85b30 @flag=:e, @raw_value="-efoo"> # ./lib/command_line_options.rb:26:in `value' # ./spec/command_line_options_spec.rb:36:in `block (3 levels) in <top (required)>' Enable Labs !90 90 @mark_menard WiteSmallThings - February 8, 2014
  • 90. # OptionWithContent def value return nil if option_unset? valid? ? extract_value_from_raw_value : nil end # IntegerOption def value return if option_unset? Integer(extract_value_from_raw_value) end Enable Labs !91 91 @mark_menard WiteSmallThings - February 8, 2014
  • 91. CommandLineOptions boolean options are true if present are false if absent string options must have content is valid when there is content can return the value return nil if not in argv integer options must have content must be an integer can return the value as an integer returns nil if not in argv ! OptionWithContent has a flag is valid when it has no raw value is valid when it has a value can return it's value when present returns nil if the flag has no raw value Enable Labs !92 92 @mark_menard WiteSmallThings - February 8, 2014
  • 92. Done! @mark_menard Enable Labs 93 WiteSmallThings - February 8, 2014
  • 93. class CommandLineOptions ! ! ! ! ! ! ! ! ! ! def initialize (argv = [], &block) @options = {} @argv = argv instance_eval &block populate_options_with_raw_values end def valid? options.values.all?(&:valid?) end def value (option_flag) options[option_flag].value end private attr_reader :options, :argv def populate_options_with_raw_values options.each do |option_flag, option| option.raw_value = raw_value_for_option(option_flag) end end def option (option_flag, option_type = :boolean) options[option_flag] = get_option_class(option_type).new(option_flag, nil) end def get_option_class (option_type) "#{option_type}_option".camelize.constantize end def raw_value_for_option (option_flag) argv.find { |arg| arg =~ /-#{option_flag}/ } end end Enable Labs !94 94 @mark_menard WiteSmallThings - February 8, 2014
  • 94. ! def valid? options.values.all?(&:valid?) end ! def value (option_flag) options[option_flag].value end Enable Labs !95 95 @mark_menard WiteSmallThings - February 8, 2014
  • 95. Then @mark_menard Enable Labs 96 WiteSmallThings - February 8, 2014
  • 96. some_ruby_program -v -efoo -i100 -afoo,bar,baz Enable Labs !97 97 @mark_menard WiteSmallThings - February 8, 2014
  • 97. describe "array options" do it "can return the value as an array" do expect(CommandLineOptions.new([ "-afoo,bar,baz" ]) { option :a, :array }.value(:a)).to eq(["foo", "bar", "baz"]) end end class ArrayOption < OptionWithContent def value return nil if option_unset? extract_value_from_raw_value.split(",") end end Enable Labs !98 98 @mark_menard WiteSmallThings - February 8, 2014
  • 98. CommandLineOptions boolean options are true if present are false if absent string options must have content is valid when there is content can return the value return nil if not in argv integer options must have content must be an integer can return the value as an integer returns nil if not in argv array options can return the value as an array ! OptionWithContent has a flag is valid when it has no raw value is valid when it has a value can return it's value when present returns nil if the flag has no raw value Enable Labs !99 99 @mark_menard WiteSmallThings - February 8, 2014
  • 99. Done! @mark_menard Enable Labs 100 WiteSmallThings - February 8, 2014
  • 100. Enable Labs Start Today @mark_menard http://www.enablelabs.com/ info@enablelabs.com 866-895-8189 @mark_menard Enable Labs 101 WiteSmallThings - February 8, 2014

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