How to handle enum values in rails 4

Question

So I have a subscription table in my database.

I would like to have a state column which will have any one of the following values

Valid
Invalid
Cancelled
In Trial
Non Renewing
Future

Can someone explain how to use these values as enum values in rails 4?

Answer 1

Credit to: https://hackhands.com/ruby-on-enums-queries-and-rails-4-1/

Declare an enum attribute where the values map to integers in the database, but can be queried by name. Example:

class Conversation < ActiveRecord::Base
  enum status: [ :active, :archived ]
end

# conversation.update! status: 0
conversation.active!
conversation.active? # => true
conversation.status  # => "active"

# conversation.update! status: 1
conversation.archived!
conversation.archived? # => true
conversation.status    # => "archived"

# conversation.update! status: 1
conversation.status = "archived"

# conversation.update! status: nil
conversation.status = nil
conversation.status.nil? # => true
conversation.status      # => nil

Scopes based on the allowed values of the enum field will be provided as well. With the above example, it will create an active and archived scope.

You can set the default value from the database declaration, like:

create_table :conversations do |t|
  t.column :status, :integer, default: 0
end

Good practice is to let the first declared status be the default.

Finally, it's also possible to explicitly map the relation between attribute and database integer with a Hash:

class Conversation < ActiveRecord::Base
  enum status: { active: 0, archived: 1 }
end

Note that when an Array is used, the implicit mapping from the values to database integers is derived from the order the values appear in the array. In the example, :active is mapped to 0 as it's the first element, and :archived is mapped to 1. In general, the i-th element is mapped to i-1 in the database.

Therefore, once a value is added to the enum array, its position in the array must be maintained, and new values should only be added to the end of the array. To remove unused values, the explicit Hash syntax should be used.

In rare circumstances you might need to access the mapping directly. The mappings are exposed through a class method with the pluralized attribute name:

Conversation.statuses # => { "active" => 0, "archived" => 1 }

Use that class method when you need to know the ordinal value of an enum:

Conversation.where("status <> ?", Conversation.statuses[:archived])

Where conditions on an enum attribute must use the ordinal value of an enum.

More info: http://api.rubyonrails.org/v4.1.0/classes/ActiveRecord/Enum.html

Answer 2

You can use gem called Workflow. It enables you to use custom statuses and gracefully handle transitions between states. I've used it on many Rails3 and Rails 4 apps.

Example from the documentation.

class Article
  include Workflow
  workflow do
    state :new do
      event :submit, :transitions_to => :awaiting_review
    end
    state :awaiting_review do
      event :review, :transitions_to => :being_reviewed
    end
    state :being_reviewed do
      event :accept, :transitions_to => :accepted
      event :reject, :transitions_to => :rejected
    end
    state :accepted
    state :rejected
  end
end

And later:

article = Article.new
article.accepted? # => false
article.new? # => true