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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'
require 'active_support/core_ext/object/blank'
require 'active_support/core_ext/class/attribute'
module ActiveRecord
# = Active Record Named \Scopes
module NamedScope
extend ActiveSupport::Concern
module ClassMethods
# Returns an anonymous \scope.
#
# posts = Post.scoped
# 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.scoped
# fruits = fruits.where(:color => 'red') if options[:red_only]
# fruits = fruits.limit(10) if limited?
#
# Anonymous \scopes tend to be useful when procedurally generating complex
# queries, where passing intermediate values (\scopes) around as first-class
# objects is convenient.
#
# You can define a \scope that applies to all finders using
# ActiveRecord::Base.default_scope.
def scoped(options = nil)
if options
scoped.apply_finder_options(options)
else
if current_scope
current_scope.clone
else
scope = relation.clone
scope.default_scoped = true
scope
end
end
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.now - 1.week)
# end
#
# The example above would be 'frozen' to the <tt>Time.now</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.now - 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, scope_options = {})
name = name.to_sym
valid_scope_name?(name)
extension = Module.new(&Proc.new) if block_given?
scope_proc = lambda do |*args|
options = scope_options.respond_to?(:call) ? scope_options.call(*args) : scope_options
options = scoped.apply_finder_options(options) if options.is_a?(Hash)
relation = scoped.merge(options)
extension ? relation.extending(extension) : relation
end
singleton_class.send(:redefine_method, name, &scope_proc)
end
protected
def valid_scope_name?(name)
if respond_to?(name, true)
logger.warn "Creating scope :#{name}. " \
"Overwriting existing method #{self.name}.#{name}."
end
end
end
end
end
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