Ruby Metaprogramming
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The document discusses Ruby metaprogramming techniques such as class variables, class inheritance, singleton classes, blocks, evaluation, dynamic method definition, mixins, monkey patching, and hooks. It provides examples of how these techniques can be combined to add dynamic behavior to classes and modules in Ruby.
![def run(&block)
block[arg1, arg2]
end](https://image.slidesharecdn.com/metaprogramming-100912125200-phpapp02/85/Ruby-Metaprogramming-30-320.jpg)
![class MyLib
NAMES = { :name => "mylib’s instance" }
def method_missing(method, *args)
if NAMES.key?(method.to_sym)
NAMES[method.to_sym]
else
super
end
end
end](https://image.slidesharecdn.com/metaprogramming-100912125200-phpapp02/85/Ruby-Metaprogramming-64-320.jpg)
![class String
def to_permalink
self.downcase.gsub(/[^[a-z0-9]-]/, "-")
end
end](https://image.slidesharecdn.com/metaprogramming-100912125200-phpapp02/85/Ruby-Metaprogramming-73-320.jpg)
Ruby Metaprogramming
- 2. @fnando
- 3. AVISOS.
- 4. TUDO É OBJETO. INCLUINDO CLASSES.
- 6. VARIÁVEIS DE CLASSE.
- 7. class MyLib @@name = "mylib" def self.name @@name end end
- 9. class MyOtherLib < MyLib @@name = "myotherlib" end
- 11. VARIÁVEIS DE CLASSE SÃO COMPARTILHADAS.
- 12. VARIÁVEIS DE INSTÂNCIA.
- 13. class MyLib @name = "mylib" def self.name @name end end
- 15. class MyOtherLib < MyLib @name = "myotherlib" end
- 17. VARIÁVEIS DE INSTÂNCIA PERTENCEM AO OBJETO.
- 18. METACLASSE.
- 19. class MyLib class << self end end
- 20. class MyLib # ruby 1.9.2+ singleton_class.class_eval do end end
- 21. class Object def singleton_class class << self; self; end end end unless Object.respond_to?(:singleton_class)
- 22. class MyLib class << self attr_accessor :name end end
- 23. MyLib.name = "mylib" MyLib.name #=> mylib
- 24. BLOCOS.
- 28. def run(&block) yield arg1, arg2 end
- 29. def run(&block) block.call(arg1, arg2) end
- 30. def run(&block) block[arg1, arg2] end
- 31. def run(&block) # ruby 1.9+ block.(arg1, arg2) end
- 32. METACLASSE, BLOCOS E VARIÁVEL DE INSTÂNCIA.
- 33. MyLib.configure do |config| config.name = "mylib" end
- 34. class MyLib class << self attr_accessor :name end def self.configure(&block) yield self end end
- 35. EVALUATION.
- 36. eval, class_eval, e instance_eval
- 37. MyLib.class_eval <<-RUBY "running inside class" RUBY #=> “running inside class”
- 38. MyLib.class_eval do "running inside class" end #=> “running inside class”
- 39. handler = proc { self.kind_of?(MyLib) } handler.call #=> false
- 40. handler = proc { self.kind_of?(MyLib) } lib.instance_eval(&handler) #=> true
- 41. BLOCOS, METACLASSE, VARIÁVEIS DE INSTÂNCIA, EVALUATION.
- 42. MyLib.configure do self.name = "mylib" name #=> “mylib” end
- 43. class MyLib class << self attr_accessor :name end def self.configure(&block) instance_eval(&block) end end
- 44. DEFINIÇÃO DE MÉTODOS.
- 45. MONKEY PATCHING.
- 46. class Integer def kbytes self * 1024 end end 128.kbytes #=> 131072
- 47. define_method.
- 48. MyLib.class_eval do define_method "name" do @name end define_method "name=" do |name| @name = name end end
- 49. lib = MyLib.new lib.name = "mynewname" lib.name #=> “mynewname”
- 50. EVALUATION.
- 51. MyLib.class_eval <<-RUBY def self.name "mylib" end def name "mylib's instance" end RUBY
- 52. MyLib.class_eval do def self.name "mylib" end def name "mylib's instance" end end
- 53. MyLib.name #=> “mylib” MyLib.new.name #=> “mylib’s instance”
- 54. BLOCOS, EVALUATION, DEFINIÇÃO DE MÉTODOS.
- 55. MyLib.class_eval do name "mylib" name #=> “mylib” end
- 56. class MyLib def self.accessor(method) class_eval <<-RUBY def self.#{method}(*args) if args.size.zero? @#{method} else @#{method} = args.last end end RUBY end accessor :name end
- 57. MyLib.class_eval do name "mylib" name #=> “mylib” end
- 58. configure do name "mylib" name #=> “mylib” end
- 59. def configure(&block) MyLib.instance_eval(&block) end
- 60. DISCLAIMER.
- 61. METHOD MISSING.
- 63. NoMethodError: undefined method ‘invalid’ for #<MyLib:0x10017e2f0>
- 64. class MyLib NAMES = { :name => "mylib’s instance" } def method_missing(method, *args) if NAMES.key?(method.to_sym) NAMES[method.to_sym] else super end end end
- 65. class MyLib #... def respond_to?(method, include_private = false) if NAMES.key?(method.to_sym) true else super end end end
- 67. MIXINS.
- 68. class MyLib extend Accessor accessor :name end class MyOtherLib extend Accessor accessor :name end
- 69. module Accessor def accessor(name) class_eval <<-RUBY def self.#{name}(*args) if args.size.zero? @#{name} else @#{name} = args.last end end RUBY end end
- 70. MONKEY PATCHING, MIXINS, EVALUATION, DYNAMIC DISPATCHING E HOOKS.
- 71. class Conference < ActiveRecord::Base has_permalink end
- 72. "welcome to QConSP".to_permalink #=> “welcome-to-qconsqp”
- 73. class String def to_permalink self.downcase.gsub(/[^[a-z0-9]-]/, "-") end end
- 74. class Conference < ActiveRecord::Base before_validation :generate_permalink def generate_permalink write_attribute :permalink, name.to_s.to_permalink end end
- 75. module Permalink end ActiveRecord::Base.send :include, Permalink
- 76. module Permalink def self.included(base) base.send :extend, ClassMethods end end
- 77. module Permalink # ... module ClassMethods def has_permalink class_eval do before_validation :generate_permalink include InstanceMethods end end end end
- 78. module Permalink # ... module InstanceMethods def generate_permalink write_attribute :permalink, name.to_s.to_permalink end end end
- 79. conf = Conference.create(:name => "QConSP 2010") conf.permalink #=> "qconsp-2010"
- 80. ENTÃO...
- 81. META PROGRAMMING É COMPLICADO.
- 82. MAS NEM TANTO.
- 83. APRENDA RUBY.
- 84. OBRIGADO.
- 85. nandovieira.com.br simplesideias.com.br spesa.com.br github.com/fnando @fnando