polymorphic_identity

polymorphic_identity dynamically generates aliases for polymorphic associations based on the class names of those associations.

Resources

API

• rdoc.info/github/pluginaweek/polymorphic_identity/master/frames

Bugs

• github.com/pluginaweek/polymorphic_identity/issues

Development

• github.com/pluginaweek/polymorphic_identity

Testing

• travis-ci.org/pluginaweek/polymorphic_identity

Source

• git://github.com/pluginaweek/polymorphic_identity.git

Mailing List

• groups.google.com/group/pluginaweek-talk

Description

Polymorphic associations are not very descriptive when it comes to easily knowing the type of model your interacting with. For example, a typical polymorphic assocation looks like the following:

class Tag < ActiveRecord::Base
  belongs_to :taggable, :polymorphic => true
end

When getting the taggable record, you would normally have to call tag.taggable. However, if you know that the taggable record is just an instance of the Article model, then it would feel more comfortable if you could just call tag.article. polymoprhic_identity makes this possible by dynamically checking the name of the polymorphic record’s class and creating methods that allow you to access the polymorphic association based on that class name.

Usage

Example

class Comment < ActiveRecord::Base
  belongs_to :commentable, :polymorphic => true
  belongs_to :commenter, :polymorphic => true
end

class Article < ActiveRecord::Base
  has_many :comments, :as => :commentable
end

class User < ActiveRecord::Base
  has_many :comments, :as => :commenter
end

c = Comment.find(1)   # => #<Tag id: 1, commentable_id: 1, commentable_type: "Article", commenter_id: 1, commenter_type: "User"}>
c.commentable         # => #<Article id: 1>
c.article             # => #<Article id: 1>
c.commenter           # => #<User id: 1>
c.user                # => #<User id: 1>

Testing

Before you can run any tests, the following gem must be installed:

• plugin_test_helper

To run against a specific version of Rails:

rake test RAILS_FRAMEWORK_ROOT=/path/to/rails

Dependencies

• Rails 2.0 or later