MetaProgram some factories

v1.rb

module ModelFactory
  def self.factory(resource, defaults = {})
    resource = resource.downcase
    defaults = defaults.dup.freeze

    resource_defaults = "default_#{resource}_attributes".to_sym
    build_resource    = "build_#{resource}".to_sym
    create_resource   = "create_#{resource}".to_sym

    define_method resource_defaults do
      defaults
    end
    module_function resource_defaults

    define_method build_resource do |opts = {}|
      opts = send(resource_defaults).merge(opts).reject{ |o| :optional == o }
      opts.each{ |k, v| opts[k] = v.call if v.is_a? Proc }
      klass = self.class.const_get(resource.to_s.classify)
      klass.new(opts)
    end
    module_function build_resource

    define_method create_resource do |opts = {}|
      send(build_resource, opts).tap{ |r| r.save! }
    end
    module_function create_resource
  end

  factory :ewok
  factory :wampa, { size: :small, fur: :brown }
  factory :jedi, lightsaber: :green, delusion_of_grandeur: :optional
  factory :rebel, { alliance: true, joined_at: ->{ 1.week.ago } }
end

v2.rb

module ModelFactory
  FactoryNotFound = Class.new(RuntimeError)
  
  def self.factories
    @factories ||= {}
  end

  def self.factory(resource, defaults = {})
    factories[resource] = defaults.dup.freeze
  end


  module_function

  def factory_defaults(resource)
    factories.fetch(resource) { raise FactoryNotFound, resource }
  end

  def build(resource, opts = {})
    opts = factory_defaults(resource).merge(opts).reject{ |o| :optional == o }
    opts.each{ |k, v| opts[k] = v.call if v.is_a? Proc }
    resource.new(opts)
  end

  def create(resource, opts = {})
    build(resource, opts).tap{ |r| r.save! }
  end

end

module ModelFactory
  factory Ewok
  factory Wampa, { size: :small, fur: :brown }
  factory Jedi, lightsaber: :green, delusion_of_grandeur: :optional
  factory Rebel, { alliance: true, joined_at: ->{ 1.week.ago } }
end