There are two versions of acts_as_taggable:

• The plugin: Acts As Taggable Plugin
• The gem: thats what this page is about!

More information on the Gem can be found here:

• RubyForge Project for acts_as_taggable Gem
• RDocs for acts_as_taggable Gem
• An excellent intro to using acts_as_taggable

Issues:

• The Gem has some issues with Rails 1.1.0, see here
  So be sure to upgrade to 1.1.2 or later!
• How To Make It Works With Postgresql
  

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This is an example how to add / edit / list tags

In the actions NEW and EDIT _form.rhtml I added a field for tags

Tags for this Item

<= text_field_tag( ‘tags’, ’’, “value” => ”#{h @item.tag_names.join(” “)}”) >

I ran into some stringify_keys! issues, which is why it’s done this way.

And my items_controller was updated with an additional line to save the tags

def update
  @item = Item.find(params[:id])
  @item.tag(params[:tags])
  if @item.update_attributes(params[:item])
    flash[:notice] = 'Item was successfully updated.'
    redirect_to :action => 'show', :id => @item
  else
    render :action => 'edit'
  end
end

and in the list:

tags for this Item: <=h @item.tag_names.join(” “) >

---

The problem with the above code is that you cannot replace tags, only add them. If you would like a tag field type of set up, do this:

class Item <ActiveRecord::Base
  def tag_text
    tag_names.join(" ")
  end
  def tag_text=(tags)
    tag(tags, :clear => true)
  end
end

Then all you need to do in the RHTML to add the field:

<= text_field 'item', 'text_tags' >

And to show:

Tags: <=h @item.text_tags >

This keeps tag hanlding transparent and out of the controller, too.

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For any googler who still want to use this gem on Rails 2.0.2 like me:

If you have an error while starting server: “no such file to load—acts-as_taggable (MissingSourceFile)” then you may need to replace the line in your environment.rb:
require ‘acts_as_taggable’
with:
require ‘taggable’

Stealth from http://www.guod.net/2008/2/24/acts_as_taggable-gem-errors