Move DefaultScope and NamedScope under Scoping

1 files changed, 202 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/scoping/named.rb b/activerecord/lib/active_record/scoping/named.rb
new file mode 100644
index 0000000000..f7512bbf5f
--- /dev/null
+++ b/activerecord/lib/active_record/scoping/named.rb
@@ -0,0 +1,202 @@
+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 Scoping
+    module Named
+      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
+
+        ##
+        # 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.clone
+            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.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
+end