Allow methods to be called from the instance in factory girl attributes

This fixes a regression introduced with the introduction of the
anonymous class.

Closes #264

lib/factory_girl/attribute_assigner.rb

@@ -8,6 +8,7 @@ module FactoryGirl
     end
 
     def object
+      @evaluator.instance = build_class_instance
       build_class_instance.tap do |instance|
         attributes_to_set_on_instance.each do |attribute|
           instance.send("#{attribute}=", get(attribute))
@@ -17,6 +18,8 @@ module FactoryGirl
     end
 
     def hash
+      @evaluator.instance = null_object.new
+
       attributes_to_set_on_hash.inject({}) do |result, attribute|
         result[attribute] = get(attribute)
         result
@@ -29,6 +32,14 @@ module FactoryGirl
       @build_class_instance ||= @build_class.new
     end
 
+    def null_object
+      Class.new(BasicObject) do
+        def method_missing(*args)
+          nil
+        end
+      end
+    end
+
     def get(attribute_name)
       @evaluator.send(attribute_name)
     end

lib/factory_girl/evaluator.rb

@@ -12,11 +12,15 @@ module FactoryGirl
 
     delegate :association, :to => :@build_strategy
 
+    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
-        super
+        @instance.send(method_name, *args, &block)
       end
     end
 

spec/acceptance/attributes_from_instance_spec.rb

@@ -0,0 +1,53 @@
+require "spec_helper"
+
+describe "calling methods on the model instance" do
+  before do
+    define_model('User', :age => :integer, :age_copy => :integer) do
+      def age
+        read_attribute(:age) || 18
+      end
+    end
+
+    FactoryGirl.define do
+      factory :user do
+        age_copy { age }
+      end
+    end
+  end
+
+  context "without the attribute being overridden" do
+    it "returns the correct value from the instance" do
+      FactoryGirl.build(:user).age_copy.should == 18
+    end
+
+    it "returns nil during attributes_for" do
+      FactoryGirl.attributes_for(:user)[:age_copy].should be_nil
+    end
+
+    it "doesn't instantiate a record with attributes_for" do
+      User.stubs(:new)
+      FactoryGirl.attributes_for(:user)
+      User.should have_received(:new).never
+    end
+  end
+
+  context "with the attribute being overridden" do
+    it "uses the overridden value" do
+      FactoryGirl.build(:user, :age_copy => nil).age_copy.should be_nil
+    end
+
+    it "uses the overridden value during attributes_for" do
+      FactoryGirl.attributes_for(:user, :age_copy => 25)[:age_copy].should == 25
+    end
+  end
+
+  context "with the referenced attribute being overridden" do
+    it "uses the overridden value" do
+      FactoryGirl.build(:user, :age => nil).age_copy.should be_nil
+    end
+
+    it "uses the overridden value during attributes_for" do
+      FactoryGirl.attributes_for(:user, :age => 25)[:age_copy].should == 25
+    end
+  end
+end