Pulled in changes from zacstewart (pull #42), but with extra documentation and test.

README.markdown

@@ -156,6 +156,7 @@ It takes four parameters:
       - this setting still works but `data-association-insertion-method` takes precedence. may be removed in a future version.
   - `partial`: explicitly declare the name of the partial that will be used
   - `render_options` : options passed through to the form-builder function (e.g. `simple_fields_for`, `semantic_fields_for` or `fields_for`).
+                       If it contains a `:locals` option containing a hash, that is handed to the partial.
 
 Optionally you could also leave out the name and supply a block that is captured to give the name (if you want to do something more complicated).
 
@@ -168,6 +169,13 @@ be handed down as follows:
 = link_to_add_association 'add something', f, :something, :render_options => {:wrapper => 'inline' }
 ````
 
+If you want to specify locals that needed to handed down to the partial, write
+
+````haml
+= link_to_add_association 'add something', f, :something, :render_options => {:locals => {:sherlock => 'Holmes' }}
+````
+
+
 #### :partial
 
 To overrule the default partial name, e.g. because it shared between multiple views, write

lib/cocoon/view_helpers.rb

@@ -33,9 +33,11 @@ module Cocoon
     # :nodoc:
     def render_association(association, f, new_object, render_options={}, custom_partial=nil)
       partial = setup_partial(custom_partial, association)
+      locals =  render_options.delete(:locals)
       method_name = f.respond_to?(:semantic_fields_for) ? :semantic_fields_for : (f.respond_to?(:simple_fields_for) ? :simple_fields_for : :fields_for)
       f.send(method_name, association, new_object, {:child_index => "new_#{association}"}.merge(render_options)) do |builder|
-        render(partial, :f => builder, :dynamic => true)
+        partial_options = {:f => builder, :dynamic => true}.merge(locals)
+        render(partial, partial_options)
       end
     end
 
@@ -46,6 +48,7 @@ module Cocoon
     # - *association* :  the associated objects, e.g. :tasks, this should be the name of the <tt>has_many</tt> relation.
     # - *html_options*:  html options to be passed to <tt>link_to</tt> (see <tt>link_to</tt>)
     #          - *:render_options* : options passed to `simple_fields_for, semantic_fields_for or fields_for`
+    #              - *:locals*     : the locals hash in the :render_options is handed to the partial
     #          - *:partial*        : explicitly override the default partial name
     # - *&block*:        see <tt>link_to</tt>
 

spec/cocoon_spec.rb

@@ -73,6 +73,18 @@ describe Cocoon do
       end
     end
 
+    context "with extra render-options to pass locals to the partial" do
+      it "uses the correct plural" do
+        @tester.unstub(:render_association)
+        @form_obj.should_receive(:fields_for) { | association, new_object, options_hash, &block| block.call }
+        @tester.should_receive(:render).with("person_fields", {:f=>nil, :dynamic=>true, :alfred=>"Judoka"}).and_return ("partiallll")
+        result = @tester.link_to_add_association('add something', @form_obj, :people, :render_options => {:wrapper => 'inline', :locals => {:alfred => 'Judoka'}})
+        result.to_s.should == '<a href="#" class="add_fields" data-association="person" data-associations="people" data-template="partiallll">add something</a>'
+      end
+    end
+
+
+
     context "when using formtastic" do
       before(:each) do
         @tester.unstub(:render_association)