Module: ActiveRecord::Scoping::Named::ClassMethods
- Defined in:
- activerecord/lib/active_record/scoping/named.rb
Instance Method Summary collapse
-
#all ⇒ Object
Returns an ActiveRecord::Relation scope object.
-
#default_extensions ⇒ Object
:nodoc:.
-
#default_scoped(scope = relation) ⇒ Object
:nodoc:.
-
#scope(name, body, &block) ⇒ Object
Adds a class method for retrieving and querying objects.
-
#scope_for_association(scope = relation) ⇒ Object
:nodoc:.
Instance Method Details
#all ⇒ Object
Returns an ActiveRecord::Relation scope object.
posts = Post.all
posts.size # Fires "select count(*) from posts" and returns the count
posts.each {|p| puts p.name } # Fires "select * from posts" and loads post objects
fruits = Fruit.all
fruits = fruits.where(color: 'red') if [:red_only]
fruits = fruits.limit(10) if limited?
You can define a scope that applies to all finders using default_scope.
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# File 'activerecord/lib/active_record/scoping/named.rb', line 25 def all scope = current_scope if scope if scope._deprecated_scope_source ActiveSupport::Deprecation.warn(<<~MSG.squish) Class level methods will no longer inherit scoping from `#{scope._deprecated_scope_source}` in Rails 6.1. To continue using the scoped relation, pass it into the block directly. To instead access the full set of models, as Rails 6.1 will, use `#{name}.unscoped`, or `#{name}.default_scoped` if a model has default scopes. MSG end if self == scope.klass scope.clone else relation.merge!(scope) end else default_scoped end end |
#default_extensions ⇒ Object
:nodoc:
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# File 'activerecord/lib/active_record/scoping/named.rb', line 60 def default_extensions # :nodoc: if scope = scope_for_association || build_default_scope scope.extensions else [] end end |
#default_scoped(scope = relation) ⇒ Object
:nodoc:
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# File 'activerecord/lib/active_record/scoping/named.rb', line 56 def default_scoped(scope = relation) # :nodoc: build_default_scope(scope) || scope end |
#scope(name, body, &block) ⇒ Object
Adds a class method for retrieving and querying objects. The method is intended to return an ActiveRecord::Relation object, which is composable with other scopes. If it returns nil
or false
, an all scope is returned instead.
A scope represents a narrowing of a database query, such as where(color: :red).select('shirts.*').includes(:washing_instructions)
.
class Shirt < ActiveRecord::Base
scope :red, -> { where(color: 'red') }
scope :dry_clean_only, -> { joins(:washing_instructions).where('washing_instructions.dry_clean_only = ?', true) }
end
The above calls to #scope define class methods Shirt.red
and Shirt.dry_clean_only
. Shirt.red
, in effect, represents the query Shirt.where(color: 'red')
.
You should always pass a callable object to the scopes defined with #scope. This ensures that the scope is re-evaluated each time it is called.
Note that this is simply ‘syntactic sugar’ for defining an actual class method:
class Shirt < ActiveRecord::Base
def self.red
where(color: 'red')
end
end
Unlike Shirt.find(...)
, however, the object returned by Shirt.red
is not an Array but an ActiveRecord::Relation, which is composable with other scopes; it resembles the association object constructed by a has_many declaration. For instance, you can invoke Shirt.red.first
, Shirt.red.count
, Shirt.red.where(size: 'small')
. Also, just as with the association objects, named scopes act like an Array, implementing Enumerable; Shirt.red.each(&block)
, Shirt.red.first
, and Shirt.red.inject(memo, &block)
all behave as if Shirt.red
really was an array.
These named scopes are composable. For instance, Shirt.red.dry_clean_only
will produce all shirts that are both red and dry clean only. Nested finds and calculations also work with these compositions: Shirt.red.dry_clean_only.count
returns the number of garments for which these criteria obtain. Similarly with Shirt.red.dry_clean_only.average(:thread_count)
.
All scopes are available as class methods on the ActiveRecord::Base descendant upon which the scopes were defined. But they are also available to has_many associations. If,
class Person < ActiveRecord::Base
has_many :shirts
end
then elton.shirts.red.dry_clean_only
will return all of Elton’s red, dry clean only shirts.
Named scopes can also have extensions, just as with has_many declarations:
class Shirt < ActiveRecord::Base
scope :red, -> { where(color: 'red') } do
def dom_id
'red_shirts'
end
end
end
Scopes can also be used while creating/building a record.
class Article < ActiveRecord::Base
scope :published, -> { where(published: true) }
end
Article.published.new.published # => true
Article.published.create.published # => true
Class methods on your model are automatically available on scopes. Assuming the following setup:
class Article < ActiveRecord::Base
scope :published, -> { where(published: true) }
scope :featured, -> { where(featured: true) }
def self.latest_article
order('published_at desc').first
end
def self.titles
pluck(:title)
end
end
We are able to call the methods like this:
Article.published.featured.latest_article
Article.featured.titles
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# File 'activerecord/lib/active_record/scoping/named.rb', line 169 def scope(name, body, &block) unless body.respond_to?(:call) raise ArgumentError, "The scope body needs to be callable." end if dangerous_class_method?(name) raise ArgumentError, "You tried to define a scope named \"#{name}\" " \ "on the model \"#{self.name}\", but Active Record already defined " \ "a class method with the same name." end if method_defined_within?(name, Relation) raise ArgumentError, "You tried to define a scope named \"#{name}\" " \ "on the model \"#{self.name}\", but ActiveRecord::Relation already defined " \ "an instance method with the same name." end valid_scope_name?(name) extension = Module.new(&block) if block if body.respond_to?(:to_proc) singleton_class.define_method(name) do |*args| scope = all._exec_scope(name, *args, &body) scope = scope.extending(extension) if extension scope end else singleton_class.define_method(name) do |*args| scope = body.call(*args) || all scope = scope.extending(extension) if extension scope end end generate_relation_method(name) end |
#scope_for_association(scope = relation) ⇒ Object
:nodoc:
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# File 'activerecord/lib/active_record/scoping/named.rb', line 48 def scope_for_association(scope = relation) # :nodoc: if current_scope&.empty_scope? scope else default_scoped(scope) end end |