update tagging model

app/models/tag.rb

@@ -1,11 +1,47 @@
-class Tag < ActiveRecord::Base
-  has_many_polymorphs :taggables,
-                      :from => [:todos, :recurring_todos], 
-                      :through => :taggings,
-                      :dependent => :destroy
-
-  def on(taggable, user)
-    tagging = taggings.create :taggable => taggable, :user => user
-  end
-
-end
+
+# The Tag model. This model is automatically generated and added to your app if
+# you run the tagging generator included with has_many_polymorphs.
+
+class Tag < ActiveRecord::Base
+
+  DELIMITER = "," # Controls how to split and join tagnames from strings. You may need to change the <tt>validates_format_of parameters</tt> if you change this.
+
+  # If database speed becomes an issue, you could remove these validations and
+  # rescue the ActiveRecord database constraint errors instead.
+  validates_presence_of :name
+  validates_uniqueness_of :name, :case_sensitive => false
+  
+  # Change this validation if you need more complex tag names.
+  validates_format_of :name, :with => /^[a-zA-Z0-9\_\-]+$/, :message => "can not contain special characters"
+  
+  # Set up the polymorphic relationship.
+  has_many_polymorphs :taggables, 
+    :from => [:todos, :recurring_todos], 
+    :through => :taggings, 
+    :dependent => :destroy,
+    :skip_duplicates => false, 
+    :parent_extend => proc {
+    # Defined on the taggable models, not on Tag itself. Return the tagnames
+    # associated with this record as a string.
+    def to_s
+      self.map(&:name).sort.join(Tag::DELIMITER)
+    end
+  }
+    
+  # Callback to strip extra spaces from the tagname before saving it. If you
+  # allow tags to be renamed later, you might want to use the
+  # <tt>before_save</tt> callback instead.
+  def before_create 
+    self.name = name.downcase.strip.squeeze(" ")
+  end
+
+  def on(taggable, user)
+    taggings.create :taggable => taggable, :user => user
+  end
+  
+  # Tag::Error class. Raised by ActiveRecord::Base::TaggingExtensions if
+  # something goes wrong.
+  class Error < StandardError
+  end
+    
+end

app/models/tagging.rb

@@ -1,11 +1,17 @@
-class Tagging < ActiveRecord::Base
-  belongs_to :tag
-  belongs_to :taggable, :polymorphic => true
-  belongs_to :user
-
-  # def before_destroy
-  #   # disallow orphaned tags
-  #   # TODO: this doesn't seem to be working
-  #   tag.destroy if tag.taggings.count < 2  
-  # end
-end
+
+# The Tagging join model. This model is automatically generated and added to your app if you run the tagging generator included with has_many_polymorphs.
+
+class Tagging < ActiveRecord::Base 
+ 
+  belongs_to :tag
+  belongs_to :taggable, :polymorphic => true
+  belongs_to :user
+  
+  # If you also need to use <tt>acts_as_list</tt>, you will have to manage the tagging positions manually by creating decorated join records when you associate Tags with taggables.
+  # acts_as_list :scope => :taggable
+    
+  # This callback makes sure that an orphaned <tt>Tag</tt> is deleted if it no longer tags anything.
+  def after_destroy
+    tag.destroy_without_callbacks if tag and tag.taggings.count == 0
+  end    
+end

lib/activerecord_base_tag_extensions.rb

@@ -1,30 +0,0 @@
-class ActiveRecord::Base
-  # These methods will work for any model instances
-  
-  # Tag with deletes all the current tags before adding the new ones
-  # This makes the edit form more intiuitive:
-  # Whatever is in the tags text field is what gets set as the tags for that action
-  # If you submit an empty tags text field, all the tags are removed.
-  def tag_with(tags, user)
-    Tag.transaction do
-      Tagging.delete_all("taggable_id = #{self.id} and taggable_type = '#{self.class}' and user_id = #{user.id}")
-      tags.downcase.split(",").each do |tag|
-        Tag.find_or_create_by_name(tag.strip).on(self, user)
-      end
-    end
-  end
-
-  def tag_list
-    tags.map(&:name).join(', ')
-  end
-  
-  def delete_tags tag_string
-     split = tag_string.downcase.split(",")
-     tags.delete tags.select{|t| split.include? t.name.strip}
-  end
-  
-  def add_tag tag_name
-    Tag.find_or_create_by_name(tag_name.strip).on(self,user)
-  end
-
-end

lib/tagging_extensions.rb

@@ -0,0 +1,147 @@
+
+class ActiveRecord::Base #:nodoc:
+
+  # These extensions make models taggable. This file is automatically generated and required by your app if you run the tagging generator included with has_many_polymorphs.
+  module TaggingExtensions
+    
+    # Add tags to <tt>self</tt>. Accepts a string of tagnames, an array of tagnames, an array of ids, or an array of Tags.
+    #
+    # We need to avoid name conflicts with the built-in ActiveRecord association methods, thus the underscores.
+    def _add_tags incoming, user
+      taggable?(true)
+      tag_cast_to_string(incoming).each do |tag_name|
+        begin
+          tag = Tag.find_or_create_by_name(tag_name).on(self,user)
+          raise Tag::Error, "tag could not be saved: #{tag_name}" if tag.new_record?
+          tag.taggables << self
+        rescue ActiveRecord::StatementInvalid => e
+          raise unless e.to_s =~ /duplicate/i
+        end
+      end
+    end
+  
+    # Removes tags from <tt>self</tt>. Accepts a string of tagnames, an array of tagnames, an array of ids, or an array of Tags.  
+    def _remove_tags outgoing, user
+      taggable?(true)
+      outgoing = tag_cast_to_string(outgoing)
+     
+      tags.delete(*(tags.select do |tag|
+        outgoing.include? tag.name    
+      end))
+      end
+
+   # Returns the tags on <tt>self</tt> as a string.
+    def tag_list
+      # Redefined later to avoid an RDoc parse error.
+    end
+  
+    # Replace the existing tags on <tt>self</tt>. Accepts a string of tagnames, an array of tagnames, an array of ids, or an array of Tags.
+    def tag_with list, user
+      #:stopdoc:
+      taggable?(true)
+      list = tag_cast_to_string(list)
+             
+      # Transactions may not be ideal for you here; be aware.
+      Tag.transaction do 
+        current = tags.map(&:name)
+        _add_tags(list - current, user)
+        _remove_tags(current - list, user)
+      end
+      
+      self
+      #:startdoc:
+    end
+
+   # Returns the tags on <tt>self</tt> as a string.
+    def tag_list #:nodoc:
+      #:stopdoc:
+      taggable?(true)
+      tags.reload
+      tags.to_s
+      #:startdoc:
+    end
+    
+    private 
+    
+    def tag_cast_to_string obj #:nodoc:
+      case obj
+        when Array
+          obj.map! do |item|
+            case item
+              when /^\d+$/, Fixnum then Tag.find(item).name # This will be slow if you use ids a lot.
+              when Tag then item.name
+              when String then item
+              else
+                raise "Invalid type"
+            end
+          end              
+        when String
+          obj = obj.split(Tag::DELIMITER).map do |tag_name| 
+            tag_name.strip.squeeze(" ")
+          end
+        else
+          raise "Invalid object of class #{obj.class} as tagging method parameter"
+      end.flatten.compact.map(&:downcase).uniq
+    end 
+  
+    # Check if a model is in the :taggables target list. The alternative to this check is to explicitly include a TaggingMethods module (which you would create) in each target model.  
+    def taggable?(should_raise = false) #:nodoc:
+      unless flag = respond_to?(:tags)
+        raise "#{self.class} is not a taggable model" if should_raise
+      end
+      flag
+    end
+
+  end
+  
+  module TaggingFinders
+    # 
+    # Find all the objects tagged with the supplied list of tags
+    # 
+    # Usage : Model.tagged_with("ruby")
+    #         Model.tagged_with("hello", "world")
+    #         Model.tagged_with("hello", "world", :limit => 10)
+    #
+    def tagged_with(*tag_list)
+      options = tag_list.last.is_a?(Hash) ? tag_list.pop : {}
+      tag_list = parse_tags(tag_list)
+      
+      scope = scope(:find)
+      options[:select] ||= "#{table_name}.*"
+      options[:from] ||= "#{table_name}, tags, taggings"
+      
+      sql  = "SELECT #{(scope && scope[:select]) || options[:select]} "
+      sql << "FROM #{(scope && scope[:from]) || options[:from]} "
+
+      add_joins!(sql, options, scope)
+      
+      sql << "WHERE #{table_name}.#{primary_key} = taggings.taggable_id "
+      sql << "AND taggings.taggable_type = '#{ActiveRecord::Base.send(:class_name_of_active_record_descendant, self).to_s}' "
+      sql << "AND taggings.tag_id = tags.id "
+      
+      tag_list_condition = tag_list.map {|t| "'#{t}'"}.join(", ")
+      
+      sql << "AND (tags.name IN (#{sanitize_sql(tag_list_condition)})) "
+      sql << "AND #{sanitize_sql(options[:conditions])} " if options[:conditions]
+      sql << "GROUP BY #{table_name}.id "
+      sql << "HAVING COUNT(taggings.tag_id) = #{tag_list.size}"
+      
+      add_order!(sql, options[:order], scope)
+      add_limit!(sql, options, scope)
+      add_lock!(sql, options, scope)
+      
+      find_by_sql(sql)
+    end
+    
+    def parse_tags(tags)
+      return [] if tags.blank?
+      tags = Array(tags).first
+      tags = tags.respond_to?(:flatten) ? tags.flatten : tags.split(Tag::DELIMITER)
+      tags.map { |tag| tag.strip.squeeze(" ") }.flatten.compact.map(&:downcase).uniq
+    end
+    
+  end
+
+  include TaggingExtensions
+  extend  TaggingFinders
+end