Build only one PartialIteration object for loop

actionview/lib/action_view/renderer/partial_renderer.rb

@@ -4,9 +4,9 @@ module ActionView
   class PartialIteration # :nodoc:
     attr_reader :size, :index
 
-    def initialize(size, index)
+    def initialize(size)
       @size  = size
-      @index = index
+      @index = 0
     end
 
     def first?
@@ -16,6 +16,10 @@ module ActionView
     def last?
       index == size - 1
     end
+
+    def iterate!
+      @index += 1
+    end
   end
 
   # = Action View Partials
@@ -412,16 +416,16 @@ module ActionView
         layout = find_template(layout, @template_keys)
       end
 
-      index = -1
+      partial_interation = PartialIteration.new(@collection.size)
-      @collection.map do |object|
+      locals[iteration] = partial_interation
-        index += 1
 
+      @collection.map do |object|
         locals[as]        = object
-        locals[counter]   = index
+        locals[counter]   = partial_interation.index
-        locals[iteration] = PartialIteration.new(@collection.size, index)
 
         content = template.render(view, locals)
         content = layout.render(view, locals) { content } if layout
+        partial_interation.iterate!
         content
       end
     end
@@ -431,17 +435,20 @@ module ActionView
       cache = {}
       keys  = @locals.keys
 
-      index = -1
+      partial_interation = PartialIteration.new(@collection.size)
+
       @collection.map do |object|
-        index += 1
+        index = partial_interation.index
         path, as, counter, iteration = collection_data[index]
 
         locals[as]        = object
         locals[counter]   = index
-        locals[iteration] = PartialIteration.new(@collection.size, index)
+        locals[iteration] = partial_interation
 
         template = (cache[path] ||= find_template(path, keys + [as, counter]))
-        template.render(view, locals)
+        content = template.render(view, locals)
+        partial_interation.iterate!
+        content
       end
     end
 

actionview/test/template/partial_iteration_test.rb

@@ -3,28 +3,31 @@ require 'action_view/renderer/partial_renderer'
 
 class PartialIterationTest < ActiveSupport::TestCase
   def test_has_size_and_index
-    iteration = ActionView::PartialIteration.new 3, 0
+    iteration = ActionView::PartialIteration.new 3
     assert_equal 0, iteration.index, "should be at the first index"
     assert_equal 3, iteration.size, "should have the size"
   end
 
   def test_first_is_true_when_current_is_at_the_first_index
-    iteration = ActionView::PartialIteration.new 3, 0
+    iteration = ActionView::PartialIteration.new 3
     assert iteration.first?, "first when current is 0"
   end
 
   def test_first_is_false_unless_current_is_at_the_first_index
-    iteration = ActionView::PartialIteration.new 3, 1
+    iteration = ActionView::PartialIteration.new 3
+    iteration.iterate!
     assert !iteration.first?, "not first when current is 1"
   end
 
   def test_last_is_true_when_current_is_at_the_last_index
-    iteration = ActionView::PartialIteration.new 3, 2
+    iteration = ActionView::PartialIteration.new 3
+    iteration.iterate!
+    iteration.iterate!
     assert iteration.last?, "last when current is 2"
   end
 
   def test_last_is_false_unless_current_is_at_the_last_index
-    iteration = ActionView::PartialIteration.new 3, 0
+    iteration = ActionView::PartialIteration.new 3
     assert !iteration.last?, "not last when current is 0"
   end
 end