From ca2fa587cf224e59f46bbeda0de538fba1cf6217 Mon Sep 17 00:00:00 2001
From: Michael Richardson <mcr@sandelman.ca>
Date: Tue, 31 Aug 2010 16:17:12 -0400
Subject: [PATCH] added tag to increment a variable each time it is referenced

---
 lib/liquid/tags/inc.rb | 37 +++++++++++++++++++++++++++++++++++++
 test/inc_tag_test.rb   | 16 ++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 lib/liquid/tags/inc.rb
 create mode 100644 test/inc_tag_test.rb

diff --git a/lib/liquid/tags/inc.rb b/lib/liquid/tags/inc.rb
new file mode 100644
index 0000000..be140c0
--- /dev/null
+++ b/lib/liquid/tags/inc.rb
@@ -0,0 +1,37 @@
+#require 'rubygems'
+#require 'ruby-debug'
+
+module Liquid
+  
+  # inc is used in a place where one needs to insert a counter
+  #     into a template, and needs the counter to survive across
+  #     multiple instantiations of the template.
+  #
+  #     if the variable does not exist, it is created with value 0.
+
+  #   Hello: {% inc variable %}
+  #
+  # gives you:
+  #
+  #    Hello: 0
+  #    Hello: 1
+  #    Hello: 2
+  #
+  class Inc < Tag
+    def initialize(tag_name, markup, tokens)      
+      @variable = markup.strip
+
+      super    
+    end    
+  
+    def render(context)
+      value = context.registers[@variable] ||= 0
+      context.registers[@variable] = value + 1
+      value.to_s
+    end
+  
+    private
+  end
+  
+  Template.register_tag('inc', Inc)
+end
diff --git a/test/inc_tag_test.rb b/test/inc_tag_test.rb
new file mode 100644
index 0000000..cb4daa7
--- /dev/null
+++ b/test/inc_tag_test.rb
@@ -0,0 +1,16 @@
+require File.dirname(__FILE__) + '/helper'
+
+
+class IncTagTest < Test::Unit::TestCase
+  include Liquid
+  
+  def test_inc
+    assert_template_result('0','{%inc port %}')  
+    assert_template_result('0 1','{%inc port %} {%inc port%}')  
+    assert_template_result('0 0 1 2 1',
+                           '{%inc port %} {%inc starboard%} ' +
+                           '{%inc port %} {%inc port%} ' +
+                           '{%inc starboard %}')
+  end
+  
+end