This plugin is based on acts_as_taggable by DHH but includes extras such as tests, smarter tag assignment, and tag cloud calculations.

gem "bborn-acts_as_taggable_on_steroids"

Generate and apply the migration:

ruby script/generate acts_as_taggable_migration
rake db:migrate

Let's suppose users have many posts and we want those posts to have tags. The first step is to add acts_as_taggable to the Post class:

class Post < ActiveRecord::Base
	acts_as_taggable

	belongs_to :user
end

We can now use the tagging methods provided by acts_as_taggable, #tag_list and #tag_list=. Both these methods work like regular attribute accessors.

p = Post.find(:first)
p.tag_list # []
p.tag_list = "Funny, Silly"
p.save
p.tag_list # ["Funny", "Silly"]

You can also add or remove arrays of tags.

p.tag_list.add("Great", "Awful")
p.tag_list.remove("Funny")

In your views you should use something like the following:

<%= f.label :tag_list %>
<%= f.text_field :tag_list, :size => 80 %>

To retrieve objects tagged with a certain tag, use find_tagged_with.

Post.tagged_with('Funny, Silly')

By default, find_tagged_with will find objects that have any of the given tags. To find only objects that are tagged with all the given tags, use match_all.

Post.tagged_with('Funny, Silly', :match_all => true)

See ActsAsTaggable::ActiveRecordExtension::InstanceMethods for more methods and options.

To construct tag clouds, the frequency of each tag needs to be calculated. Because we specified acts_as_taggable on the Post class, we can get a calculation of all the tag counts by using Post.tag_counts. But what if we wanted a tag count for an single user's posts? To achieve this we call tag_counts on the association:

User.find(:first).posts.tag_counts

A helper is included to assist with generating tag clouds. Include it in your helper file:

module ApplicationHelper
  include TagsHelper
end

You can also use the counts method on Tag to get the counts for all tags in the database.

Tag.counts

Here is an example that generates a tag cloud.

Controller:

class PostController < ApplicationController
  def tag_cloud
    @tags = Post.tag_counts
  end
end

View:

<% tag_cloud @tags, %w(css1 css2 css3 css4) do |tag, css_class| %>
  <%= link_to tag.name, { :action => :tag, :id => tag.name }, :class => css_class %>
<% end %>

CSS:

.css1 { font-size: 1.0em; }
.css2 { font-size: 1.2em; }
.css3 { font-size: 1.4em; }
.css4 { font-size: 1.6em; }

It is useful to cache the list of tags to reduce the number of queries executed. To do this, add a column named cached_tag_list to the model which is being tagged. The column should be long enough to hold the full tag list and must have a default value of null, not an empty string.

class CachePostTagList < ActiveRecord::Migration
  def self.up
    add_column :posts, :cached_tag_list, :string
  end
end

class Post < ActiveRecord::Base
  acts_as_taggable

  # The caching column defaults to cached_tag_list, but can be changed:
  # 
  # set_cached_tag_list_column_name "my_caching_column_name"
end

The details of the caching are handled for you. Just continue to use the tag_list accessor as you normally would. Note that the cached tag list will not be updated if you directly create Tagging objects or manually append to the tags or taggings associations. To update the cached tag list you should call save_cached_tag_list manually.

If you want to change the delimiter used to parse and present tags, set TagList.delimiter. For example, to use spaces instead of commas, add the following to your application.rb:

TagList.delimiter = " "

Set Tag.destroy_unused to remove tags when they are no longer being used to tag any objects. Defaults to false.

Tag.destroy_unused = true