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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 <tt>ActiveRecord::Relation</tt> 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
# ActiveRecord::Base.default_scope.
def all
if current_scope
current_scope.clone
else
scope = relation
scope.default_scoped = true
scope
end
end
##
# Collects attributes from scopes that should be applied when creating
# an AR instance for the particular class this is called on.
def scope_attributes # :nodoc:
if current_scope
current_scope.scope_for_create
else
scope = relation
scope.default_scoped = true
scope.scope_for_create
end
end
##
# Are there default attributes associated with this scope?
def scope_attributes? # :nodoc:
current_scope || default_scopes.any?
end
# Adds a class method for retrieving and querying objects. A \scope represents a narrowing of a database query,
# such as <tt>where(:color => :red).select('shirts.*').includes(:washing_instructions)</tt>.
#
# 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 <tt>scope</tt> define class methods Shirt.red and Shirt.dry_clean_only. Shirt.red,
# in effect, represents the query <tt>Shirt.where(:color => 'red')</tt>.
#
# 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 <tt>Shirt.find(...)</tt>, however, the object returned by Shirt.red is not an Array; it
# resembles the association object constructed by a <tt>has_many</tt> declaration. For instance,
# you can invoke <tt>Shirt.red.first</tt>, <tt>Shirt.red.count</tt>, <tt>Shirt.red.where(:size => 'small')</tt>.
# Also, just as with the association objects, named \scopes act like an Array, implementing Enumerable;
# <tt>Shirt.red.each(&block)</tt>, <tt>Shirt.red.first</tt>, and <tt>Shirt.red.inject(memo, &block)</tt>
# all behave as if Shirt.red really was an Array.
#
# These named \scopes are composable. For instance, <tt>Shirt.red.dry_clean_only</tt> will produce
# all shirts that are both red and dry clean only.
# Nested finds and calculations also work with these compositions: <tt>Shirt.red.dry_clean_only.count</tt>
# returns the number of garments for which these criteria obtain. Similarly with
# <tt>Shirt.red.dry_clean_only.average(:thread_count)</tt>.
#
# All \scopes are available as class methods on the ActiveRecord::Base descendant upon which
# the \scopes were defined. But they are also available to <tt>has_many</tt> associations. If,
#
# class Person < ActiveRecord::Base
# has_many :shirts
# end
#
# then <tt>elton.shirts.red.dry_clean_only</tt> will return all of Elton's red, dry clean
# only shirts.
#
# Named \scopes can also be procedural:
#
# class Shirt < ActiveRecord::Base
# scope :colored, lambda { |color| where(:color => color) }
# end
#
# In this example, <tt>Shirt.colored('puce')</tt> finds all puce shirts.
#
# On Ruby 1.9 you can use the 'stabby lambda' syntax:
#
# scope :colored, ->(color) { where(:color => color) }
#
# Note that scopes defined with \scope will be evaluated when they are defined, rather than
# when they are used. For example, the following would be incorrect:
#
# class Post < ActiveRecord::Base
# scope :recent, where('published_at >= ?', Time.current - 1.week)
# end
#
# The example above would be 'frozen' to the <tt>Time.current</tt> value when the <tt>Post</tt>
# class was defined, and so the resultant SQL query would always be the same. The correct
# way to do this would be via a lambda, which will re-evaluate the scope each time
# it is called:
#
# class Post < ActiveRecord::Base
# scope :recent, lambda { where('published_at >= ?', Time.current - 1.week) }
# end
#
# Named \scopes can also have extensions, just as with <tt>has_many</tt> 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
# map(&: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)
extension = Module.new(&block) if block
# Check body.is_a?(Relation) to prevent the relation actually being
# loaded by respond_to?
if body.is_a?(Relation) || !body.respond_to?(:call)
ActiveSupport::Deprecation.warn(
"Using #scope without passing a callable object is deprecated. For " \
"example `scope :red, where(color: 'red')` should be changed to " \
"`scope :red, -> { where(color: 'red') }`. There are numerous gotchas " \
"in the former usage and it makes the implementation more complicated " \
"and buggy. (If you prefer, you can just define a class method named " \
"`self.red`.)"
)
end
singleton_class.send(:define_method, name) do |*args|
options = body.respond_to?(:call) ? unscoped { body.call(*args) } : body
relation = all.merge(options)
extension ? relation.extending(extension) : relation
end
end
end
end
end
end
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