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module ActiveRecord
module NamedScope
# All subclasses of ActiveRecord::Base have two named \scopes:
# * <tt>all</tt> - which is similar to a <tt>find(:all)</tt> query, and
# * <tt>scoped</tt> - which allows for the creation of anonymous \scopes, on the fly: <tt>Shirt.scoped(:conditions => {:color => 'red'}).scoped(:include => :washing_instructions)</tt>
#
# These anonymous \scopes tend to be useful when procedurally generating complex queries, where passing
# intermediate values (scopes) around as first-class objects is convenient.
def self.included(base)
base.class_eval do
extend ClassMethods
named_scope :scoped, lambda { |scope| scope }
end
end
module ClassMethods
def scopes
read_inheritable_attribute(:scopes) || write_inheritable_attribute(:scopes, {})
end
# Adds a class method for retrieving and querying objects. A scope represents a narrowing of a database query,
# such as <tt>:conditions => {:color => :red}, :select => 'shirts.*', :include => :washing_instructions</tt>.
#
# class Shirt < ActiveRecord::Base
# named_scope :red, :conditions => {:color => 'red'}
# named_scope :dry_clean_only, :joins => :washing_instructions, :conditions => ['washing_instructions.dry_clean_only = ?', true]
# end
#
# The above calls to <tt>named_scope</tt> define class methods Shirt.red and Shirt.dry_clean_only. Shirt.red,
# in effect, represents the query <tt>Shirt.find(:all, :conditions => {:color => 'red'})</tt>.
#
# 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.find(:first)</tt>, <tt>Shirt.red.count</tt>,
# <tt>Shirt.red.find(:all, :conditions => {: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 descendent 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
# named_scope :colored, lambda { |color|
# { :conditions => { :color => color } }
# }
# end
#
# In this example, <tt>Shirt.colored('puce')</tt> finds all puce shirts.
#
# Named \scopes can also have extensions, just as with <tt>has_many</tt> declarations:
#
# class Shirt < ActiveRecord::Base
# named_scope :red, :conditions => {:color => 'red'} do
# def dom_id
# 'red_shirts'
# end
# end
# end
#
#
# For testing complex named \scopes, you can examine the scoping options using the
# <tt>proxy_options</tt> method on the proxy itself.
#
# class Shirt < ActiveRecord::Base
# named_scope :colored, lambda { |color|
# { :conditions => { :color => color } }
# }
# end
#
# expected_options = { :conditions => { :colored => 'red' } }
# assert_equal expected_options, Shirt.colored('red').proxy_options
def named_scope(name, options = {}, &block)
name = name.to_sym
scopes[name] = lambda do |parent_scope, *args|
Scope.new(parent_scope, case options
when Hash
options
when Proc
options.call(*args)
end, &block)
end
(class << self; self end).instance_eval do
define_method name do |*args|
scopes[name].call(self, *args)
end
end
end
end
class Scope
attr_reader :proxy_scope, :proxy_options
NON_DELEGATE_METHODS = %w(nil? send object_id class extend find size count sum average maximum minimum paginate first last empty? any? respond_to?).to_set
[].methods.each do |m|
unless m =~ /^__/ || NON_DELEGATE_METHODS.include?(m.to_s)
delegate m, :to => :proxy_found
end
end
delegate :scopes, :with_scope, :to => :proxy_scope
def initialize(proxy_scope, options, &block)
[options[:extend]].flatten.each { |extension| extend extension } if options[:extend]
extend Module.new(&block) if block_given?
@proxy_scope, @proxy_options = proxy_scope, options.except(:extend)
end
def reload
load_found; self
end
def first(*args)
if args.first.kind_of?(Integer) || (@found && !args.first.kind_of?(Hash))
proxy_found.first(*args)
else
find(:first, *args)
end
end
def last(*args)
if args.first.kind_of?(Integer) || (@found && !args.first.kind_of?(Hash))
proxy_found.last(*args)
else
find(:last, *args)
end
end
def size
@found ? @found.length : count
end
def empty?
@found ? @found.empty? : count.zero?
end
def respond_to?(method, include_private = false)
super || @proxy_scope.respond_to?(method, include_private)
end
def any?
if block_given?
proxy_found.any? { |*block_args| yield(*block_args) }
else
!empty?
end
end
protected
def proxy_found
@found || load_found
end
private
def method_missing(method, *args, &block)
if scopes.include?(method)
scopes[method].call(self, *args)
else
with_scope :find => proxy_options, :create => proxy_options[:conditions].is_a?(Hash) ? proxy_options[:conditions] : {} do
method = :new if method == :build
proxy_scope.send(method, *args, &block)
end
end
end
def load_found
@found = find(:all)
end
end
end
end
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