Similar Models

Adds a similar_{model name plural} method to an active record model, but can be set to any name using as: {method name}. It returns the most similar models of the same class based on associated models in common.

The association(s) have to be many to many, so either habtm or has_many :through.

Add this line to your application's Gemfile:

gem 'similar_models'

And then execute:

$ bundle

Or install it yourself as:

$ gem install similar_models

Post example

class Post < ActiveRecord::Base
  has_many :author_posts
  has_many :authors, through: :author_posts
  has_and_belongs_to_many :tags

  has_similar_models :authors
  has_similar_models :tags, as: :similar_posts_by_tag
  has_similar_models :authors, :tags, as: :similar_posts_by_author_and_tag
end

class Tag < ActiveRecord::Base
end

class Author < ActiveRecord::Base
  has_many :author_posts
end

class AuthorPosts < ActiveRecord::Base
  belongs_to :author
  belongs_to :post
end

To return the posts with the most authors in common with post in descending order:

post.similar_posts

The returned object is an ActiveRecord::Relation and so chaining of other query methods is possible:

post.similar_posts.where('posts.created_at > ?', 10.days.ago).limit(5)

To return the posts with the most tags in common with post in descending order:

post.similar_posts_by_tag

To return the posts with the most authors and tags in common with post in descending order:

post.similar_posts_by_author_and_tag

The count of the associated models in common is accessible on each returned model:

post.similar_posts_model_count
post.similar_posts_by_tag_model_count
post.similar_posts_by_author_and_tag_model_count

Note multiple associations do not work with sqlite.

Because of the use of group, pagination is not supported.

If you use mbleigh/acts-as-taggable-on and want to find related users say across multiple contexts:

user.similar_users.where(taggings: { context: %w(skills interests) })

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request