require "active_support/core_ext/array"
require "active_support/core_ext/hash/except"
require "active_support/core_ext/kernel/singleton_class"
module ActiveRecord
# = Active Record \Named \Scopes
module Scoping
module Named
extend ActiveSupport::Concern
module ClassMethods
# 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 options[:red_only]
# fruits = fruits.limit(10) if limited?
#
# You can define a scope that applies to all finders using
# {default_scope}[rdoc-ref:Scoping::Default::ClassMethods#default_scope].
def all
if current_scope
current_scope.clone
else
default_scoped
end
end
def scope_for_association(scope = relation) # :nodoc:
current_scope = self.current_scope
if current_scope && current_scope.empty_scope?
scope
else
default_scoped(scope)
end
end
def default_scoped(scope = relation) # :nodoc:
build_default_scope(scope) || scope
end
def default_extensions # :nodoc:
if scope = current_scope || build_default_scope
scope.extensions
else
[]
end
end
# 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}[rdoc-ref:Scoping::Named::ClassMethods#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}[rdoc-ref:Associations::ClassMethods#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}[rdoc-ref:Associations::ClassMethods#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}[rdoc-ref:Associations::ClassMethods#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
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
valid_scope_name?(name)
extension = Module.new(&block) if block
if body.respond_to?(:to_proc)
singleton_class.send(:define_method, name) do |*args|
scope = all.scoping { instance_exec(*args, &body) }
scope = scope.extending(extension) if extension
scope || all
end
else
singleton_class.send(:define_method, name) do |*args|
scope = all.scoping { body.call(*args) }
scope = scope.extending(extension) if extension
scope || all
end
end
end
private
def valid_scope_name?(name)
if respond_to?(name, true) && logger
logger.warn "Creating scope :#{name}. " \
"Overwriting existing method #{self.name}.#{name}."
end
end
end
end
end
end