How do we define enums? Pretty much like

class Book < ActiveRecord::Base
  enum status: [:proposed, :written, :published]
end

Here what is the value of status for newly created object of class Book? It would be proposed, as is the first value from enums. What if we need a default enum value to be set to newly created objects?

Well we can achieve it using database default value constraint, but it will not be assigned until object is saved to database i.e. Book.new.status will not reflect database default-value constraint as it is yet to be saved to database.

• Rails 6.1 added support to define default value for enum. Declaring like

class Book < ActiveRecord::Base
  enum status: [:proposed, :written, :published], _default: :published
end

So now new object of class Book will show value for column status as published and not proposed.

Book.new.status # => "published"

• More example

class Blog < ActiveRecord::Base
  enum status: [:open, :inprogress, :complete], _default: :inprogress
end

Blog.new.status # => "inprogress"

Thanks for reading.

---

References -

• Rails master PR which adds _default enum by kamipo