Overview

Prim gives you the power to assign and manage the primary member of any Rails one–to–many or many–to–many assocation. And it's really simple to get started! Let's say we needed to model a User who could have several Languages:

class User < ActiveRecord::Base
  has_many :user_languages
  has_many :languages, through: :user_languages

  ...
end

class UserLanguage < ActiveRecord::Base
  belongs_to :user
  belongs_to :language

  ...
end

class Language < ActiveRecord::Base
  has_many :user_languages
  has_many :users, through: :user_languages

  ...
end

Great! Now let's say we've added a specific set of Languages. Our Users can now have new Language associations by simply creating a record in the user_languages mapping table, relating a User and a Language. But what if we want to know which of a User's Languages is their most important? Well, we could add a sort_order or primary column to the user_languages table, but then we'll need to write code to manage it all.

Enter Prim. Add

gem 'prim'

to your Gemfile. With Prim we can just add a line of code to the User model...

class User < ActiveRecord::Base
  ...

  has_primary :language
end

...and run a migration:

class AddPrimaryToUserLanguages < ActiveRecord::Migration
  def change
    add_column :user_languages, :primary, :boolean, { default: false }
  end
end

And we're done! Now we can set any User's primary language...

User.first.primary_language = Language.where( name: "English" )

...and retrieve it:

User.first.primary_language
=> #<Language id: 5, name: "English" ... >

Notes

• Currently only supports ActiveRecord with an SQL data store like PostgreSQL, MySQL, or MariaDB. More support coming soon.
• Primary management is automatically added to subclasses of ActiveRecord::Base, so your data models need to inherit from that.
• At the very least Prim requires ActiveRecord 3.2 and ActiveSupport 3.2.

Contributing

Want to contribute? Find a TODO or Github issue and take care of it! Or suggest a feature or file a bug on the issues page. Just pack up your commits by rebasing them, then submit a pull request!