Evaulate dynamic attribute blocks without arguments in the context of the proxy

lib/factory_girl/attribute/dynamic.rb

@@ -8,7 +8,7 @@ module FactoryGirl
       end
 
       def add_to(proxy)
-        value = @block.arity.zero? ? @block.call : @block.call(proxy)
+        value = @block.arity == 1 ? @block.call(proxy) : proxy.instance_eval(&@block)
         if FactoryGirl::Sequence === value
           raise SequenceAbuseError
         end

spec/acceptance/acceptance_spec.rb

@@ -8,8 +8,7 @@ describe "integration" do
         first_name 'Jimi'
         last_name  'Hendrix'
         admin       false
-        # TODO: evaluate in context of proxy
-        email {|a| "#{a.first_name}.#{a.last_name}@example.com".downcase }
+        email { "#{first_name}.#{last_name}@example.com".downcase }
 
         # TODO: nested factories
 

spec/factory_girl/attribute/dynamic_spec.rb

@@ -27,6 +27,17 @@ describe FactoryGirl::Attribute::Dynamic do
     @proxy.should have_received.set(:user, @proxy)
   end
 
+  it "evaluates the block with in the context of the proxy without an argument" do
+    result = 'other attribute value'
+    @block = lambda { other_attribute }
+    @attr  = FactoryGirl::Attribute::Dynamic.new(:user, @block)
+    @proxy = "proxy"
+    stub(@proxy).set
+    stub(@proxy).other_attribute { result }
+    @attr.add_to(@proxy)
+    @proxy.should have_received.set(:user, result)
+  end
+
   it "should raise an error when defining an attribute writer" do
     lambda {
       FactoryGirl::Attribute::Dynamic.new('test=', nil)