Ruby，使用“？” - db 或 model 方法？

Question

I love using the? for boolean fields, eg, for 'animals' table "alive?" is very obvious. Where do I define this? Do I name the db field with it when creating the table migration(don't think so). Or is it automatic for boolean fields or do I have a little method in the active record model class for animals that says something like def alive? if alive then true else false end?

Answer 1

Rails automatically generates a method ending in a ? for each of the fields in a model. Some examples:

Animal #=> Animal(id: integer, alive: boolean, name: string)
a = Animal.new

a.alive #=> nil
a.alive? #=> false
a.alive = true
a.alive? #=> true

a.name #=> nil
a.name? #=> false
a.name = "Giraffe"
a.name? #=> true

Also note that you can easily define your own ? methods:

class Animal
  def young?
    created_at > 1.day.ago
  end
end

Answer 2

This behaviour is automatic for all boolean fields in ActiveRecord.

As an extra nicety, I like to name boolean fields with an is_ prefix. is_alive , giving you is_alive? .