Base class is implied when calling .new within initialize_with

Closes #343

GETTING_STARTED.md

@@ -723,7 +723,7 @@ factory :user do
   end
 
   email
-  initialize_with { User.new(name) }
+  initialize_with { new(name) }
 end
 
 FactoryGirl.build(:user).name # Bob Hope
@@ -745,6 +745,22 @@ You can override the initializer in order to:
 * Use a method other than `new` to instantiate the instance
 * Do crazy things like decorate the instance after it's built
 
+When using `initialize_with`, you don't have to declare the class itself when
+calling `new`; however, any other class methods you want to call will have to
+be called on the class explicitly.
+
+For example:
+
+```ruby
+factory :user do
+  ignore do
+    name { Faker::Name.name }
+  end
+
+  initialize_with { User.build_with_name(name) }
+end
+```
+
 Custom Strategies
 -----------------
 

lib/factory_girl/evaluator.rb

@@ -17,7 +17,8 @@ module FactoryGirl
       undef_method(method) unless method =~ /^__|initialize/
     end
 
-    def initialize(build_strategy, overrides = {})
+    def initialize(build_class, build_strategy, overrides = {})
+      @build_class       = build_class
       @build_strategy    = build_strategy
       @overrides         = overrides
       @cached_attributes = overrides
@@ -27,6 +28,8 @@ module FactoryGirl
       end
     end
 
+    delegate :new, to: :@build_class
+
     def association(factory_name, overrides = {})
       strategy_override = overrides.fetch(:strategy) { FactoryGirl.strategy_by_name(:create) }
 

lib/factory_girl/factory.rb

@@ -32,7 +32,7 @@ module FactoryGirl
 
       strategy = strategy_class.new
 
-      evaluator = evaluator_class.new(strategy, overrides.symbolize_keys)
+      evaluator = evaluator_class.new(build_class, strategy, overrides.symbolize_keys)
       attribute_assigner = AttributeAssigner.new(evaluator, build_class, &instance_builder)
 
       evaluation = Evaluation.new(attribute_assigner, to_create)

spec/acceptance/initialize_with_spec.rb

@@ -145,3 +145,29 @@ describe "initialize_with parent and child factories" do
     FactoryGirl.build(:super_awesome).name.should == "Super"
   end
 end
+
+describe "initialize_with implicit constructor" do
+  before do
+    define_class("Awesome") do
+      attr_reader :name
+
+      def initialize(name)
+        @name = name
+      end
+    end
+
+    FactoryGirl.define do
+      factory :awesome do
+        ignore do
+          name "Great"
+        end
+
+        initialize_with { new(name) }
+      end
+    end
+  end
+
+  it "instantiates the correct object" do
+    FactoryGirl.build(:awesome, name: "Awesome name").name.should == "Awesome name"
+  end
+end

spec/factory_girl/evaluator_class_definer_spec.rb

@@ -7,7 +7,7 @@ describe FactoryGirl::EvaluatorClassDefiner do
 
   let(:attributes)    { [simple_attribute, relative_attribute, attribute_that_raises_a_second_time] }
   let(:class_definer) { FactoryGirl::EvaluatorClassDefiner.new(attributes, FactoryGirl::Evaluator) }
-  let(:evaluator)     { class_definer.evaluator_class.new(stub("build strategy", add_observer: true)) }
+  let(:evaluator)     { class_definer.evaluator_class.new(Object, stub("build strategy", add_observer: true)) }
 
   it "returns an evaluator when accessing the evaluator class" do
     evaluator.should be_a(FactoryGirl::Evaluator)