= acts_as_taggable_on_steroids

Based on the plugin by Jonathan Viney, this scopes the tags per project.

---

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  Email address: [email protected]
  
== Instructions

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

== Installation

  ruby script/plugin install http://svn.viney.net.nz/things/rails/plugins/acts_as_taggable_on_steroids

== Usage

=== Prepare database

Generate and apply the migration:

  ruby script/generate acts_as_taggable_migration
  rake db:migrate

=== Basic tagging

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, <tt>#tag_list</tt> and <tt>#tag_list=</tt>. 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")

=== Finding tagged objects

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

  Post.find_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.find_tagged_with('Funny, Silly', :match_all => true)
  
See <tt>ActiveRecord::Acts::Taggable::InstanceMethods</tt> for more methods and options.

=== Tag cloud calculations

To construct tag clouds, the frequency of each tag needs to be calculated.
Because we specified +acts_as_taggable+ on the <tt>Post</tt> class, we can
get a calculation of all the tag counts by using <tt>Post.tag_counts</tt>. 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 <tt>counts</tt> method on <tt>Tag</tt> 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; }

=== Caching

It is useful to cache the list of tags to reduce the number of queries executed. To do this,
add a column named <tt>cached_tag_list</tt> 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
<tt>tags</tt> or <tt>taggings</tt> associations. To update the cached tag list you should call <tt>save_cached_tag_list</tt> manually.

=== Delimiter

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 config/environment.rb:

  TagList.delimiter = " "

=== Unused tags

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

=== Other

Problems, comments, and suggestions all welcome. [email protected]