default_scope

Use this macro in your model to set a default scope for all operations on the model.

class Article < ActiveRecord::Base
  default_scope { where(published: true) }
end

Article.all # => SELECT * FROM articles WHERE published = true

The default_scope is also applied while creating/building a record. It is not applied while updating a record.

Article.new.published    # => true
Article.create.published # => true

(You can also pass any object which responds to call to the default_scope macro, and it will be called when building the default scope.)

If you use multiple default_scope declarations in your model then they will be merged together:

class Article < ActiveRecord::Base
  default_scope { where(published: true) }
  default_scope { where(rating: 'G') }
end

Article.all # => SELECT * FROM articles WHERE published = true AND rating = 'G'

This is also the case with inheritance and module includes where the parent or module defines a default_scope and the child or including class defines a second one.

If you need to do more complex things with a default scope, you can alternatively define it as a class method:

class Article < ActiveRecord::Base
  def self.default_scope
    # Should return a scope, you can call 'super' here etc.
  end
end

# File activerecord/lib/active_record/scoping/default.rb, line 83
        def default_scope(scope = nil)
          scope = Proc.new if block_given?

          if scope.is_a?(Relation) || !scope.respond_to?(:call)
            raise ArgumentError,
              "Support for calling #default_scope without a block is removed. For example instead "                "of `default_scope where(color: 'red')`, please use "                "`default_scope { where(color: 'red') }`. (Alternatively you can just redefine "                "self.default_scope.)"
          end

          self.default_scopes += [scope]
        end