set-a-default-scope.md

Set a Default Scope

ActiveRecord provides default_scope, which you can use to control how records are returned. An example:

# app/model/chapter.rb
class Chapter < ActiveRecord::Base
  default_scope { order(:title) }
end

Now, instead of this (ordered by ID):

Chapter.all.pluck(:title).take(5)
=> ["BALINESE CAUSE",
"BUILDING RAT",
"TAIL",
"LILAC MERCURY",
"PUMP SQUARE"]

We get this:

Chapter.all.pluck(:title).take(5)
=> ["AFGHANISTAN COAT",
"ALCOHOL GONG",
"ANTARCTICA BULL",
"ASPARAGUS",
"BALINESE CAUSE"]

Beware, this decision can lead to inexplicable behavior down the road. Use with caution.

One use case I've heard is soft deletes. We might not want soft-deleted records appearing in .all:

# app/model/chapter.rb
class Chapter < ActiveRecord::Base
  default_scope { where('soft_deleted is false') }
end

h/t Brian Dunn