Allow fields_for on a nested_attributes association to accept an expl…

…icit collection to be used. [#2648 state:resolved]

Signed-off-by: Eloy Duran <eloy.de.enige@gmail.com>

actionpack/lib/action_view/helpers/form_helper.rb

@@ -449,6 +449,15 @@ def apply_form_for_options!(object_or_array, options) #:nodoc:
       #     <% end %>
       #   <% end %>
       #
+      # Or a collection to be used:
+      #
+      #   <% form_for @person, :url => { :action => "update" } do |person_form| %>
+      #     ...
+      #     <% person_form.fields_for :projects, @active_projects do |project_fields| %>
+      #       Name: <%= project_fields.text_field :name %>
+      #     <% end %>
+      #   <% end %>
+      #
       # When projects is already an association on Person you can use
       # +accepts_nested_attributes_for+ to define the writer method for you:
       #
@@ -1037,18 +1046,21 @@ def nested_attributes_association?(association_name)
 
         def fields_for_with_nested_attributes(association_name, args, block)
           name = "#{object_name}[#{association_name}_attributes]"
-          association = @object.send(association_name)
-          explicit_object = args.first.to_model if args.first.respond_to?(:to_model)
+          association = args.first.to_model if args.first.respond_to?(:to_model)
+
+          if association.respond_to?(:new_record?)
+            association = [association] if @object.send(association_name).is_a?(Array)
+          elsif !association.is_a?(Array)
+            association = @object.send(association_name)
+          end
 
           if association.is_a?(Array)
-            children = explicit_object ? [explicit_object] : association
             explicit_child_index = args.last[:child_index] if args.last.is_a?(Hash)
-
-            children.map do |child|
+            association.map do |child|
               fields_for_nested_model("#{name}[#{explicit_child_index || nested_child_index(name)}]", child, args, block)
             end.join
-          else
-            fields_for_nested_model(name, explicit_object || association, args, block)
+          elsif association
+            fields_for_nested_model(name, association, args, block)
           end
         end
 

actionpack/test/template/form_helper_test.rb

@@ -784,6 +784,42 @@ def test_nested_fields_for_with_existing_and_new_records_on_a_nested_attributes_
     assert_dom_equal expected, output_buffer
   end
 
+  def test_nested_fields_for_with_an_empty_supplied_attributes_collection
+    form_for(:post, @post) do |f|
+      concat f.text_field(:title)
+      f.fields_for(:comments, []) do |cf|
+        concat cf.text_field(:name)
+      end
+    end
+
+    expected = '<form action="http://www.example.com" method="post">' +
+               '<input name="post[title]" size="30" type="text" id="post_title" value="Hello World" />' +
+               '</form>'
+
+    assert_dom_equal expected, output_buffer
+  end
+
+  def test_nested_fields_for_with_existing_records_on_a_supplied_nested_attributes_collection
+    @post.comments = Array.new(2) { |id| Comment.new(id + 1) }
+
+    form_for(:post, @post) do |f|
+      concat f.text_field(:title)
+      f.fields_for(:comments, @post.comments) do |cf|
+        concat cf.text_field(:name)
+      end
+    end
+
+    expected = '<form action="http://www.example.com" method="post">' +
+               '<input name="post[title]" size="30" type="text" id="post_title" value="Hello World" />' +
+               '<input id="post_comments_attributes_0_id" name="post[comments_attributes][0][id]" type="hidden" value="1" />' +
+               '<input id="post_comments_attributes_0_name" name="post[comments_attributes][0][name]" size="30" type="text" value="comment #1" />' +
+               '<input id="post_comments_attributes_1_id" name="post[comments_attributes][1][id]" type="hidden" value="2" />' +
+               '<input id="post_comments_attributes_1_name" name="post[comments_attributes][1][name]" size="30" type="text" value="comment #2" />' +
+               '</form>'
+
+    assert_dom_equal expected, output_buffer
+  end
+
   def test_nested_fields_for_on_a_nested_attributes_collection_association_yields_only_builder
     @post.comments = [Comment.new(321), Comment.new]
     yielded_comments = []