thoughtbot--factory_bot/lib/factory_girl/evaluator.rb

require "active_support/core_ext/hash/except"
require "active_support/core_ext/class/attribute"

module FactoryGirl
  class Evaluator
    class_attribute :callbacks, :attribute_lists

    def self.attribute_list
      AttributeList.new.tap do |list|
        attribute_lists.each do |attribute_list|
          list.apply_attributes attribute_list.to_a
        end
      end
    end

    private_instance_methods.each do |method|
      undef_method(method) unless method =~ /^__|initialize/
    end

    def initialize(build_strategy, overrides = {})
      @build_strategy    = build_strategy
      @overrides         = overrides
      @cached_attributes = overrides

      @overrides.each do |name, value|
        singleton_class.send :define_method, name, lambda { value }
      end

      @build_strategy.add_observer(CallbackRunner.new(self.class.callbacks, self))
    end

    def association(factory_name, overrides = {})
      build_strategy = if overrides.has_key?(:strategy)
                         overrides[:strategy]
                       else
                         Strategy::Create
                       end

      build_strategy = StrategyCalculator.new(build_strategy).strategy
      runner = FactoryRunner.new(factory_name, build_strategy, [overrides.except(:strategy)])
      @build_strategy.association(runner)
    end

    def instance=(object_instance)
      @instance = object_instance
    end

    def method_missing(method_name, *args, &block)
      if @cached_attributes.key?(method_name)
        @cached_attributes[method_name]
      else
        @instance.send(method_name, *args, &block)
      end
    end

    def __overrides
      @overrides
    end

    private

    class CallbackRunner
      def initialize(callbacks, evaluator)
        @callbacks = callbacks
        @evaluator = evaluator
      end

      def update(name, result_instance)
        @callbacks.select {|callback| callback.name == name }.each do |callback|
          callback.run(result_instance, @evaluator)
        end
      end
    end
  end
end