JoinCollection

Join an array of mongoid docs with target objects by specified relation and delegation fields

Add this line to your application's Gemfile:

gem 'join_collection'

And then execute:

$ bundle

Or install it yourself as:

$ gem install join_collection

The class JoinCollection itself is a wrapper around an array of mongoid docs, so to initialize it, simply put

user_collection = JoinCollection.new(users) # where users is an array of mongoid docs

We will call what we put inside the initilizer the source objects.

To use any of the join_* functions, make sure you provide the following parameters.

1. The 1st parameter is the target_name, which is used as the prefix for the delegation fields.
2. The 2nd parameter is the target_class, which is used to query target objects.
3. The 3rd parameter is the options, which is not optional and it must be a hash containing a :relation key and a :delegation key.

• The key :relation points to another hash, which specifies the foreign key to primary key for the type of join relation.
• The key :delegation also points to a hash, which specifies the :fields of the target object to be delegated to the doc in the source objects. In a has_many relation, you can also privide a :if conditional block to specify which target object to delegate if there are many target objects.

Assume we have a user belongs_to site relationship, and the Site class has the field url.

user_collection = JoinCollection.new(users)
user_collection.join_to(:site, Site, :relation => {:site_id => :id}, :delegation => {:fields => [:url]})

After this, all the source objects, the users, in the user_collection will have the field site_url

user_collection.source_objects.first.site_url   # => "http://..."

Assume we have a user has_one profile relationship, and the Profile class has the field twitter.

user_collection = JoinCollection.new(users)
user_collection.join_one(:profile, Profile, :relation => {:user_id => :id}, :delegation => {:fields => [:twitter]})

After this, all the source objects, the users, in the user_collection will have the field profile_twitter

user_collection.source_objects.first.profile_twitter   # => "https://twitter.com/..."

Assume we have a user has_many contacts relationship, and the Contact class has the field phone.

user_collection = JoinCollection.new(users)
user_collection.join_many(:contacts, Contact, :relation => {:user_id => :id},
  :delegation => {:if => lambda { |x| x.is_active? }, :fields => [:phone]})

After this, all the source objects, the users, in the user_collection will have the field contact_phone

user_collection.source_objects.first.contact_phone   # => "0987-654-321"

If you specify a delegation field which is identical to the target name of that join type, the whole object(s) will be captured.

user_collection.join_to(:site, Site, :relation => {:site_id => :id}, :delegation => {:fields => [:site]})
user_collection.source_objects.first.site   # get the site the user belongs to

user_collection.join_one(:profile, Profile, :relation => {:user_id => :id}, :delegation => {:fields => [:profile]})
user_collection.source_objects.first.profile   # get the profile the user has

user_collection.join_many(:contacts, Contact, :relation => {:user_id => :id}, :delegation => {:fields => [:contacts]})
user_collection.source_objects.first.contacts   # get all contacts the user has

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