Rails 3 inspired modularity

modular-classes.rb

# Making a large class modular
# * Put core functionality into Base module inside your class
# * Split other functionality into modules and include them at the bottom of the
#   your class
# * Now it is easy to reuse or recreate custom versions of the class by creating
#   new classes, including only some modules, swapping modules out for others, etc.
class MainClass
  module Base
    attr_accessor :name
    def initialize(name)
      @name = name
    end
  end

  module Upcase
    def initialize(first)
      super
      @name.upcase!
    end
  end

  module Title
    def initialize(name)
      super
      @name = "Mr. #{@name}"
    end
  end
  
  include Base
  include Upcase
  include Title
end

# This is the cool part. You can use the parts of this class like legos to
# create your own customized version

class MyCustomClassWithJustBase
  include MainClass::Base
end

class MyCustomClassWithNoUpcase
  include MainClass::Base
  include MainClass::Title
end

class MyCustomClassWithUpcaseLast
  include MainClass::Base
  include MainClass::Title
  include MainClass::Upcase
end

# Examples

puts MainClass.new("anderson").name                    # => Mr. ANDERSON
puts MyCustomClassWithJustBase.new("anderson").name    # => anderson
puts MyCustomClassWithNoUpcase.new("anderson").name    # => Mr. anderson
puts MyCustomClassWithUpcaseLast.new("anderson").name  # => MR. ANDERSON

# Ancestry

p MyCustomClassWithJustBase.ancestors
# => [MyCustomClassWithJustBase, MainClass::Base, Object, Kernel]

p MyCustomClassWithNoUpcase.ancestors
# => [MyCustomClassWithNoUpcase, MainClass::Title, MainClass::Base, Object, Kernel]

p MyCustomClassWithJustBase.ancestors
# => [MyCustomClassWithJustBase, MainClass::Base, Object, Kernel]

p MainClass.ancestors
# => [MainClass, MainClass::Title, MainClass::Upcase, MainClass::Base, Object, Kernel]