the new and create actions will now build the resource with attributes based on ability conditions hash - closes #114

lib/cancan/ability.rb

@@ -206,6 +206,14 @@ module CanCan
       message.blank? ? nil : message
     end
 
+    def attributes_for(action, subject)
+      attributes = {}
+      relevant_can_definitions(action, subject).map do |can_definition|
+        attributes.merge!(can_definition.new_attributes) if can_definition.base_behavior
+      end
+      attributes
+    end
+
     private
 
     def unauthorized_message_keys(action, subject)

lib/cancan/can_definition.rb

@@ -67,6 +67,14 @@ module CanCan
       hash
     end
 
+    def new_attributes
+      attributes = {}
+      @conditions.each do |key, value|
+        attributes[key] = value unless [Array, Range, Hash].include? value.class
+      end
+      attributes
+    end
+
     private
 
     def subject_class?(subject)

lib/cancan/controller_resource.rb

@@ -51,7 +51,15 @@ module CanCan
 
     def build_resource
       method_name = @options[:singleton] ? "build_#{name}" : "new"
-      resource_base.send(*[method_name, @params[name]].compact)
+      resource = resource_base.send(*[method_name, @params[name]].compact)
+      initial_attributes.each do |name, value|
+        resource.send("#{name}=", value)
+      end
+      resource
+    end
+
+    def initial_attributes
+      @controller.current_ability.attributes_for(@params[:action].to_sym, resource_class)
     end
 
     def find_resource

spec/cancan/ability_spec.rb

@@ -257,6 +257,14 @@ describe CanCan::Ability do
     @ability.can?(:read, 123 => Range).should be_true
   end
 
+  it "should have initial attributes based on hash conditions of 'new' action" do
+    @ability.can :manage, Range, :foo => "foo", :hash => {:skip => "hashes"}
+    @ability.can :create, Range, :bar => 123, :array => %w[skip arrays]
+    @ability.can :new, Range, :baz => "baz", :range => 1..3
+    @ability.cannot :new, Range, :ignore => "me"
+    @ability.attributes_for(:new, Range).should == {:foo => "foo", :bar => 123, :baz => "baz"}
+  end
+
   describe "unauthorized message" do
     after(:each) do
       I18n.backend = nil

spec/cancan/controller_resource_spec.rb

@@ -5,6 +5,7 @@ describe CanCan::ControllerResource do
     @params = HashWithIndifferentAccess.new(:controller => "abilities")
     @controller = Object.new # simple stub for now
     stub(@controller).params { @params }
+    stub(@controller).current_ability.stub!.attributes_for { {} }
   end
 
   it "should load the resource into an instance variable if params[:id] is specified" do
@@ -47,12 +48,16 @@ describe CanCan::ControllerResource do
     @controller.instance_variable_get(:@ability).should == :some_resource
   end
 
-  it "should build a new resource with no arguments if attribute hash isn't specified" do
+  it "should build a new resource with attributes from current ability" do
+    @params[:controller] = "people"
     @params[:action] = "new"
-    mock(Ability).new { :some_resource }
+    person = Object.new
+    mock(Person).new { person }
+    mock(person).name = "foobar"
+    stub(@controller).current_ability.stub!.attributes_for(:new, Person) { {:name => "foobar"} }
     resource = CanCan::ControllerResource.new(@controller)
     resource.load_resource
-    @controller.instance_variable_get(:@ability).should == :some_resource
+    @controller.instance_variable_get(:@person).should == person
   end
 
   it "should not build a resource when on index action" do