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A tagging lib for Mongoid that allows for custom tagging along dynamic contexts. This gem was originally based on mongoid_taggable by Wilker LĂșcio and Ches Martin. It has evolved substantially since that point, but all credit goes to them for the initial tagging functionality.

For instance, in a social network, a user might have tags that are called skills, interests, sports, and more. There is no real way to differentiate between tags and so an implementation of this type is not possible with mongoid_taggable.

Another example, aggregation such as counting tag occurrences was achieved by map-reduce with mongoid_taggable. It was ok for small amount of tags, but when the amount of tags and documents grow, the original mongoid_taggable won't be able to scale to real-time statistics demand.

Enter mongoid_taggable_with_context. Rather than tying functionality to a specific keyword (namely "tags"), mongoid_taggable_with_context allows you to specify an arbitrary number of tag contexts that can be used locally or in combination in the same way mongoid_taggable was used.

mongoid_taggable_with_context also provides flexibility on aggregation strategy. In addition to the map-reduce strategy, this gem also comes with real-time strategy. By using real-time strategy, your document can quickly adjusts the aggregation collection whenever tags are inserted or removed with $inc operator. So performance won't be impacted as the number of tags and documents grow.


You can simply install from rubygems:

gem install mongoid_taggable_with_context

or in Gemfile:

gem 'mongoid_taggable_with_context'

The "taggable" Macro Function

Use the taggable macro function in your model to declare a tags field. Specify field name for tags, and options for tagging behavior.


   class Article
     include Mongoid::Document
     include Mongoid::TaggableWithContext
     taggable :keywords, separator: ' ', default: ['foobar']
  • @param [ Symbol ] field

(Optional) The name of the field for tags. Defaults to "tags"

  • @param [ Hash ] options

(Optional) Options for taggable behavior.

* `@option [ String ] :separator`

    The delimiter used when converting the tags to and from String format. Defaults to " "

* `@option [ :Symbol ] :group_by_field`

    The Mongoid field to group by when RealTimeGroupBy aggregation is used.

* `@option [ <various> ] :default, :as, :localize, etc.`

    Options for Mongoid #field method will be automatically passed
    to the underlying Array field (with the exception of `:type`,
    which is coerced to `Array`).

Example Usage

To make a document taggable you need to include Mongoid::TaggableOnContext into your document and call the taggable macro with optional arguments:

class Post
  include Mongoid::Document
  include Mongoid::TaggableWithContext

  field :title
  field :content

  # default context is 'tags'.
  # This creates #tags, #tags=, #tag_string instance methods
  # separator is " " by default
  # #tags method returns an array of tags
  # #tags= methods accepts an array of tags or a separated string
  # #tag_string method returns a separated string

  # tagging for 'skills' context.
  # This creates #skills, #skills=, #skills_string instance methods
  # changing tag separator to "," (Default is " ")
  taggable :skills, separator: ','

  # aliased context tagging.
  # This creates #interests, #interests=, #interests_string instance methods
  # The tags will be stored in a database field called 'ints'
  taggable :ints, as: :interests

Then in your form, for example:

<% form_for @post do |f| %>
    <%= f.label :title %><br />
    <%= f.text_field :title %>
    <%= f.label :content %><br />
    <%= f.text_area :content %>
    <%= f.label :tags %><br />
    <%= text_field_tag 'post[tags]' %>
    <%= f.label :interests %><br />
    <%= text_field_tag 'post[interests]' %>
    <%= f.label :skills %><br />
    <%= text_field_tag 'post[skills]' %>
    <button type="submit">Send</button>
<% end %>

Aggregation Strategies

By including an aggregation strategy in your document, tag aggregations will be automatically available to you. This lib presents the following aggregation strategies:

  • MapReduce
  • RealTime
  • RealTimeGroupBy

The following document will automatically aggregate counts on all tag contexts.

class Post
  include Mongoid::Document
  include Mongoid::TaggableWithContext

  # automatically adds real time aggregations to all tag contexts
  include Mongoid::TaggableWithContext::AggregationStrategy::RealTime

  # alternatively for map-reduce
  # include Mongoid::TaggableWithContext::AggregationStrategy::MapReduce

  field :title
  field :content

  taggable :skills, separator: ','
  taggable :ints, as: interests

When you include an aggregation strategy, your document also gains a few extra methods to retrieve aggregation data. In the case of previous example the following methods are included:


Here is how to use these methods in more detail:

Post.create!(tags: "food,ant,bee")
Post.create!(tags: "juice,food,bee,zip")
Post.create!(tags: "honey,strip,food")

Post.tags # will retrieve ["ant", "bee", "food", "honey", "juice", "strip", "zip"]
Post.tags_with_weight # will retrieve:
# [
#   ['ant', 1],
#   ['bee', 2],
#   ['food', 3],
#   ['honey', 1],
#   ['juice', 1],
#   ['strip', 1],
#   ['zip', 1]
# ]

Contributing to mongoid_taggable_with_context

  • Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet
  • Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it
  • Fork the project
  • Start a feature/bugfix branch
  • Commit and push until you are happy with your contribution
  • Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
  • Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.

Copyright (c) 2011 Aaron Qian. See LICENSE.txt for further details.