module ActiveRecord module NamedScope # All subclasses of ActiveRecord::Base have one named scope: # * scoped - which allows for the creation of anonymous \scopes, on the fly: Shirt.scoped(:conditions => {:color => 'red'}).scoped(:include => :washing_instructions) # # These 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 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 :conditions => {:color => :red}, :select => 'shirts.*', :include => :washing_instructions. # # 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 named_scope define class methods Shirt.red and Shirt.dry_clean_only. Shirt.red, # in effect, represents the query Shirt.find(:all, :conditions => {:color => 'red'}). # # Unlike Shirt.find(...), however, the object returned by Shirt.red is not an Array; it resembles the association object # constructed by a has_many declaration. For instance, you can invoke Shirt.red.find(:first), Shirt.red.count, # Shirt.red.find(:all, :conditions => {: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 be procedural: # # class Shirt < ActiveRecord::Base # named_scope :colored, lambda { |color| # { :conditions => { :color => color } } # } # end # # In this example, Shirt.colored('puce') finds all puce shirts. # # Named \scopes can also have extensions, just as with has_many 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 # proxy_options 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 case parent_scope when Scope with_scope(:find => parent_scope.proxy_options) { options.call(*args) } else options.call(*args) end 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, :current_scoped_methods_when_defined 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 ||= {} [options[:extend]].flatten.each { |extension| extend extension } if options[:extend] extend Module.new(&block) if block_given? unless Scope === proxy_scope @current_scoped_methods_when_defined = proxy_scope.send(:current_scoped_methods) end @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] : {}}, :reverse_merge) do method = :new if method == :build if current_scoped_methods_when_defined with_scope current_scoped_methods_when_defined do proxy_scope.send(method, *args, &block) end else proxy_scope.send(method, *args, &block) end end end end def load_found @found = find(:all) end end end end