Merge pull request #4226 from grentis/content_for_with_flush

content_for with flush parameter

actionpack/lib/action_view/helpers/capture_helper.rb

@@ -110,7 +110,7 @@ def capture(*args)
       # That will place +script+ tags for your default set of JavaScript files on the page;
       # this technique is useful if you'll only be using these scripts in a few views.
       #
-      # Note that content_for concatenates the blocks it is given for a particular
+      # Note that content_for concatenates (default) the blocks it is given for a particular
       # identifier in order. For example:
       #
       #   <% content_for :navigation do %>
@@ -127,16 +127,37 @@ def capture(*args)
       #
       #   <ul><%= content_for :navigation %></ul>
       #
+      # If the flush parameter is true content_for replaces the blocks it is given. For example:
+      #
+      #   <% content_for :navigation do %>
+      #     <li><%= link_to 'Home', :action => 'index' %></li>
+      #   <% end %>
+      #
+      #   <%#  Add some other content, or use a different template: %>
+      #
+      #   <% content_for :navigation, true do %>
+      #     <li><%= link_to 'Login', :action => 'login' %></li>
+      #   <% end %>
+      #
+      # Then, in another template or layout, this code would render only the last link:
+      #
+      #   <ul><%= content_for :navigation %></ul>
+      #
       # Lastly, simple content can be passed as a parameter:
       #
       #   <% content_for :script, javascript_include_tag(:defaults) %>
       #
       # WARNING: content_for is ignored in caches. So you shouldn't use it
       # for elements that will be fragment cached.
-      def content_for(name, content = nil, &block)
+      def content_for(name, content = nil, flush = false, &block)
         if content || block_given?
-          content = capture(&block) if block_given?
-          @view_flow.append(name, content) if content
+          if block_given?
+            flush = content if content
+            content = capture(&block)
+          end
+          if content
+            flush ? @view_flow.set(name, content) : @view_flow.append(name, content)
+          end
           nil
         else
           @view_flow.get(name)

actionpack/test/template/capture_helper_test.rb

@@ -53,6 +53,13 @@ def test_content_for_with_multiple_calls
     assert_equal 'foobar', content_for(:title)
   end
 
+  def test_content_for_with_multiple_calls_and_flush
+    assert ! content_for?(:title)
+    content_for :title, 'foo'
+    content_for :title, 'bar', true
+    assert_equal 'bar', content_for(:title)
+  end
+
   def test_content_for_with_block
     assert ! content_for?(:title)
     content_for :title do
@@ -63,6 +70,39 @@ def test_content_for_with_block
     assert_equal 'foobar', content_for(:title)
   end
 
+  def test_content_for_with_block_and_multiple_calls_with_flush
+    assert ! content_for?(:title)
+    content_for :title do
+      'foo'
+    end
+    content_for :title, true do
+      'bar'
+    end
+    assert_equal 'bar', content_for(:title)
+  end
+
+  def test_content_for_with_block_and_multiple_calls_with_flush_nil_content
+    assert ! content_for?(:title)
+    content_for :title do
+      'foo'
+    end
+    content_for :title, nil, true do
+      'bar'
+    end
+    assert_equal 'bar', content_for(:title)
+  end
+
+  def test_content_for_with_block_and_multiple_calls_without_flush
+    assert ! content_for?(:title)
+    content_for :title do
+      'foo'
+    end
+    content_for :title, false do
+      'bar'
+    end
+    assert_equal 'foobar', content_for(:title)
+  end
+
   def test_content_for_with_whitespace_block
     assert ! content_for?(:title)
     content_for :title, 'foo'
@@ -74,12 +114,27 @@ def test_content_for_with_whitespace_block
     assert_equal 'foobar', content_for(:title)
   end
 
+  def test_content_for_with_whitespace_block_and_flush
+    assert ! content_for?(:title)
+    content_for :title, 'foo'
+    content_for :title, true do
+      output_buffer << "  \n  "
+      nil
+    end
+    content_for :title, 'bar', true
+    assert_equal 'bar', content_for(:title)
+  end
+
   def test_content_for_returns_nil_when_writing
     assert ! content_for?(:title)
     assert_equal nil, content_for(:title, 'foo')
     assert_equal nil, content_for(:title) { output_buffer << 'bar'; nil }
     assert_equal nil, content_for(:title) { output_buffer << "  \n  "; nil }
     assert_equal 'foobar', content_for(:title)
+    assert_equal nil, content_for(:title, 'foo', true)
+    assert_equal nil, content_for(:title, true) { output_buffer << 'bar'; nil }
+    assert_equal nil, content_for(:title, true) { output_buffer << "  \n  "; nil }
+    assert_equal 'bar', content_for(:title)
   end
 
   def test_content_for_question_mark