Question

I love using the ? for boolean fields, e.g, 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