thiagoa

class Imageable < Module
  def initialize(has_one: %i(main_image))
    has_one.each do |image_kind|
      define_method image_kind do
        images.find { |image| image.kind == 'main_image' }
      end
    end
  end

  def included(model_class)

thiagoa

class ModuleGenerator < Module
  def build_methods(methods)
    module_eval do
      methods.each do |method|
        define_method(method) do
          puts "#{method} was defined in the instance methods"
        end
      end
    end
  end

thiagoa

module OneTwoThree
  def one
    puts 'one was defined as an instance method'
  end
  
  def two
    puts 'two was defined as an instance method'
  end
  
  def three

thiagoa

OneTwoThree = Module.new do
  def one
    puts 'one was defined as an instance method'
  end
  
  def two
    puts 'two was defined as an instance method'
  end
  
  def three

thiagoa

class DynamicModuleGenerator < Module
  def initialize(methods)
    module_eval do
      methods.each do |method|
        define_method(method) do
          puts "#{method} was defined as an instance method"
        end
      end
    end
  end

thiagoa

class Module < Object
  def module_eval
    # Only the language has the magic to make this work...
  end
  
  # Imagine there are a bunch of other instance methods here.
  # Module.new generates objects that respond to these methods.
end

thiagoa

UselessAble.module_eval do
  # This is written in the module's instance methods collection
  def guess_what?
    puts "I'm useless!"
  end
end

def UselessAble.who?
  puts 'I am an abstract behavior, but I do exist somehow!'
end

thiagoa

asshole_1 = AssHole.new
asshole_1.guess_what? #=> outputs "I'm useless!"
asshole_1.soul #=> outputs "I have no soul!"

asshole_2 = AssHole.new
asshole_2.guess_what? #=> outputs "I'm useless!"
asshole_2.soul #=> outputs "I have no soul!"

thiagoa

module UselessAble
  def guess_what?
    puts "I'm useless!"
  end
end

# Instances of AssHole now respond to "guess_what?" and "soul"
class AssHole
  include UselessAble

thiagoa

# Instances of Project respond to every method of Imageable!
class Project
  include Imageable
end

# Provides the same collection of methods as Imageable
module SuperImageable
  include Imageable
end