From a26aff7bb19cd5b3c8a419626574872e8c62f511 Mon Sep 17 00:00:00 2001
From: Chris Kalafarski <chris@farski.com>
Date: Sun, 18 Jan 2009 20:44:41 -0500
Subject: [PATCH] add content_tag_if

---
 actionpack/lib/action_view/helpers/tag_helper.rb |   38 ++++++++++++++++++++++
 actionpack/test/template/tag_helper_test.rb      |   12 +++++++
 2 files changed, 50 insertions(+), 0 deletions(-)

diff --git a/actionpack/lib/action_view/helpers/tag_helper.rb b/actionpack/lib/action_view/helpers/tag_helper.rb
index af8c4d5..3cd7701 100644
--- a/actionpack/lib/action_view/helpers/tag_helper.rb
+++ b/actionpack/lib/action_view/helpers/tag_helper.rb
@@ -79,6 +79,44 @@ module ActionView
         end
       end
 
+      # Works much like the standard content_tag, but will pick between the specified options depending on whether the 
+      # provided condition is met. This can be used, for instance, to easily switch between classes on an HTML
+      # element depending on a given value or the current action or controller.
+      # 
+      # ==== Options
+      # Options is required, and can be defined as in content_tag for attributes that do not change with the +condition+. For those
+      # +options+ that will switch, either an array or hash can be passed. With an array, the first value will be used
+      # when +condition+ is true, and the last will be used when it is not. With a hash, the keys :if and :else are 
+      # used to define the binary options.
+      # 
+      # ==== Examples
+      #   content_tag_if(true, :p, 'Hello world!', :class => ['when-true', 'when-false'])
+      #   # => <p class="when-true">Hello world!</p>
+      #   content_tag_if(false, :p, 'Hello world!', :class => ['when-true', 'when-false'])
+      #   # => <p class="when-false">Hello world!</p>
+      # 
+      #   # on /books/10/edit
+      #   <% content_tag_if(current_page?(:controller => 'books'), :li, :id => 'book-nav', :class => { :if => 'current', :else => '' }) do -%>
+      #     <%= link_to 'Book list', books_path %>
+      #   <% end -%>
+      #   # => <li class="current" id="book-nav"><a href="/books">Book list</a></li>
+      def content_tag_if(condition, name, content_or_options_with_block, options = nil, escape = true, &block)
+    
+        options = content_or_options_with_block if content_or_options_with_block.is_a?(Hash) if block_given?
+    
+        options.each do |option, values|      
+          options[option] = case values
+            when Array then values.send(condition ? "first" : "last")
+            when Hash then ((values[:if] && values[:else]) ? values[(condition ? :if : :else)] : values.to_s)
+            else values.to_s
+          end
+        end
+    
+        content_or_options_with_block, options = options, nil if block_given?
+    
+        content_tag(name, content_or_options_with_block, options, escape, &block)   
+      end
+
       # Returns a CDATA section with the given +content+.  CDATA sections
       # are used to escape blocks of text containing characters which would
       # otherwise be recognized as markup. CDATA sections begin with the string
diff --git a/actionpack/test/template/tag_helper_test.rb b/actionpack/test/template/tag_helper_test.rb
index ef88cae..56d592a 100644
--- a/actionpack/test/template/tag_helper_test.rb
+++ b/actionpack/test/template/tag_helper_test.rb
@@ -70,6 +70,18 @@ class TagHelperTest < ActionView::TestCase
     content_tag("p") { concat content_tag("b", "Hello") }
     assert_equal '<p><b>Hello</b></p>', output_buffer
   end
+  
+  def test_content_tag_if_when_condition_is_met
+    assert_equal %(<p class="when-true">Hello world!</p>), content_tag_if(true, :p, 'Hello world!', :class => ['when-true', 'when-false'])
+    assert_equal %(<p class="when-true" id="the_id">Hello world!</p>), content_tag_if(true, :p, 'Hello world!', :id => 'the_id', :class => ['when-true', 'when-false'])
+    assert_equal %(<p class="when-true">Hello world!</p>), content_tag_if(true, :p, 'Hello world!', :class => {:if => 'when-true', :else => 'when-false'})
+  end
+  
+  def test_content_tag_if_when_condition_is_not_met
+    assert_equal %(<p class="when-false">Hello world!</p>), content_tag_if(false, :p, 'Hello world!', :class => ['when-true', 'when-false'])
+    assert_equal %(<p class="when-false" id="the_id">Hello world!</p>), content_tag_if(false, :p, 'Hello world!', :id => 'the_id', :class => ['when-true', 'when-false'])
+    assert_equal %(<p class="when-false">Hello world!</p>), content_tag_if(false, :p, 'Hello world!', :class => {:if => 'when-true', :else => 'when-false'})
+  end
 
   def test_cdata_section
     assert_equal "<![CDATA[<hello world>]]>", cdata_section("<hello world>")
-- 
1.6.1