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The simplest way to handle the primary or default flag to your Rails models
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README.md

SetAsPrimary

Build Status Maintainability Test Coverage

Demo Rails application | Source code of Demo Rails application

The simplest way to handle the primary or default flag to your Rails models.

Features:

  • Supports single model (without association), model with (belongs_to) association, and even polymorphic associations
  • Force primary
  • Supports PostgreSQL's unique partial index (constraint)
  • Supports PostgreSQL, MySQL, and SQLite

Installation

Add this line to your application's Gemfile:

gem 'set_as_primary'

And then execute:

$ bundle

Or install it yourself as:

$ gem install set_as_primary

Usage

In your Rails application, you might have models like EmailAddress, PhoneNumber, Address, etc., which belong to the User/Person model or polymorphic model. There, you might need to set a primary email address, primary phone number, or default address for a user, and this gem helps you to do that.

It also supports a single model with no association context.

Examples:

class User < ApplicationRecord
  has_many :email_addresses
  has_many :addresses, as: :owner
end

class EmailAddress < ApplicationRecord
  include SetAsPrimary
  belongs_to :user

  set_as_primary :primary, owner_key: :user
 end

class Address < ApplicationRecord
  include SetAsPrimary
  belongs_to :owner, polymorphic: true

  set_as_primary :primary, owner_key: :owner
end

# Single model with no owner/association context.
class Post < ApplicationRecord
  include SetAsPrimary
  
  set_as_primary :primary
end

You need to include SetAsPrimary module in your model where you want to handle the primary flag. Then to set_as_primary class helper method, pass your primary flag attribute. You might need to pass association key owner_key if you wan to consider owner (association) context.

Note: Default primary flag attribute is primary, and you can use another one too like default but make sure that flag should be present in the table and should be a boolean data type column.

Migration

If your table does not have the primary flag column, then you can add it by running following command in your rails project:

rails generate set_as_primary your_table_name flag_name

Example:

If you want to add a primary column to your posts table, then you can run command like this:

rails generate set_as_primary posts primary

Then migration gets created like this:

class AddPrimaryColumnToPosts < ActiveRecord::Migration[6.0]
  def change
    add_column :posts, :primary, :boolean, default: false, null: false
    # NOTE: Please uncomment following line if you want only one 'true' (constraint) in the table.
    # add_index :posts, :primary, unique: true, where: "(posts.primary IS TRUE)"
  end
end

If you want to create a primary column to email_addresses table, then you can run command like this:

rails generate set_as_primary email_addresses primary user

Then it creates migration like this:

class AddPrimaryColumnToEmailAddresses < ActiveRecord::Migration[6.0]
  def change
    add_column :email_addresses, :primary, :boolean, default: false, null: false
    # NOTE: Please uncomment following line if you want only one 'true' (constraint) in the table.
    # add_index :email_addresses, %i[user_id primary], unique: true, where: "(email_addresses.primary IS TRUE)"
  end
end

You might have seen extra commented lines there. These lines are there for handling the unique constraint. Currently, these lines get created only for PostgreSQL adapter as it supports partial index.

Please note that here we have passed an extra option user in the command that is nothing but the owner/association name. This extra option helps to handle the unique partial index.

Note: Partial indexes are only supported for PostgreSQL and SQLite 3.8.0+. But I also found that SQLite gives an error so currently this gem only supports PostgreSQL's unique partial index constraint.

Even if we don't have constraint (only one 'true' constraint in the table), this gem takes care of it so don't worry about the constraint.

Once migration file gets created, don't forget to run rails db:migrate to create an actual column in the table.

force_primary

class Address < ApplicationRecord
  include SetAsPrimary
  belongs_to :user

  set_as_primary :default, owner_key: :user, force_primary: false
 end

By default force_primary option is set to true. If this option is true, then it automatically sets record as primary when there is only one record in the table. If you don't want this flow, then set it as false.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/mechanicles/set_as_primary. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

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