git-svn clone http://svn.viney.net.nz/things/rails/plugins/acts_as_taggable_on_steroids in 'upstream' branch; my changes in 'master'
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README

= acts_as_taggable_on_steroids

If you find this plugin useful, please consider a donation to show your support!

  http://www.paypal.com/cgi-bin/webscr?cmd=_send-money
  
  Email address: jonathan.viney@gmail.com
  
== 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

=== How case insensitive is it?

When a tag is first created, will it will be saved with the exact name (including case) that is provided.

After that, however, the tag will be searched for and compared insensitively. If you try to add the same tag but with different case, it will not
change the case; it will add it with the original case. (So make sure you enter it correctly to begin with, or provide a way to rename tags.
But be aware that renaming it for one user will rename it for all users.)

irb -> run.tag_list = 'l'

irb -> run.save_tags; run.reload.tag_list
    => ["l"]

# Case insensitive -- will detect that you've already 'L' (even though it's spelled 'l')
# Once a tag is created, its case will never change simply by people adding/removing the tag with different spellings.
irb -> run.tag_list = 'L'

irb -> run.save_tags; run.reload.tag_list
    => ["l"]

# You'd have to explicitly update its name to change its case...
irb -> Tag.find_by_name('l').update_attribute :name, 'L'
    => true

# Case insensitive; can still be found with 'l'
irb -> Tag.find_by_name('l')
    => #<Tag id: 6, name: "L">

=== Contributing

Pull requests welcome at http://github.com/TylerRick/acts_as_taggable_on_steroids/tree/master