Added support for counter_cache columns

lib/awesome_nested_set/awesome_nested_set.rb

@@ -31,6 +31,9 @@ module NestedSet #:nodoc:
       #   child objects are destroyed alongside this object by calling their destroy
       #   method. If set to :delete_all (default), all the child objects are deleted
       #   without calling their destroy method.
+      # * +:counter_cache+ adds a counter cache for the number of children.
+      #   defaults to false.
+      #   Example: <tt>acts_as_nested_set :counter_cache => :children_count</tt>
       #
       # See CollectiveIdea::Acts::NestedSet::Model::ClassMethods for a list of class methods and
       # CollectiveIdea::Acts::NestedSet::Model::InstanceMethods for a list of instance methods added
@@ -41,6 +44,7 @@ def acts_as_nested_set(options = {})
           :left_column => 'lft',
           :right_column => 'rgt',
           :dependent => :delete_all, # or :destroy
+          :counter_cache => false
         }.merge(options)
 
         if options[:scope].is_a?(Symbol) && options[:scope].to_s !~ /_id$/
@@ -55,7 +59,8 @@ def acts_as_nested_set(options = {})
         extend Columns
 
         belongs_to :parent, :class_name => self.base_class.to_s,
-          :foreign_key => parent_column_name
+          :foreign_key => parent_column_name,
+          :counter_cache => options[:counter_cache]
         has_many :children, :class_name => self.base_class.to_s,
           :foreign_key => parent_column_name, :order => quoted_left_column_name
 

spec/awesome_nested_set_spec.rb

@@ -8,7 +8,7 @@
 
 describe "AwesomeNestedSet" do
   before(:all) do
-    self.class.fixtures :categories, :departments, :notes
+    self.class.fixtures :categories, :departments, :notes, :things
   end
 
   describe "defaults" do
@@ -791,4 +791,33 @@ def check_structure(entries, structure)
       categories(:child_3).save.should be_true
     end
   end
+
+  describe "counter_cache" do
+
+    it "should allow use of a counter cache for children" do
+      note1 = things(:parent1)
+      assert_equal 2, note1.children.count
+    end
+
+    it "should increment the counter cache on create" do
+      ActiveRecord::Base.logger.info 'FOO'
+      note1 = things(:parent1)
+      assert_equal 2, note1.children.count
+      assert_equal 2, note1[:children_count]
+      note1.children.create :body => 'Child 3'
+      assert_equal 3, note1.children.count
+      note1.reload
+      assert_equal 3, note1[:children_count]
+    end
+
+    it "should decrement the counter cache on destroy" do
+      note1 = things(:parent1)
+      assert_equal 2, note1.children.count
+      assert_equal 2, note1[:children_count]
+      note1.children.last.destroy
+      assert_equal 1, note1.children.count
+      note1.reload
+      assert_equal 1, note1[:children_count]
+    end
+  end
 end

spec/db/schema.rb

@@ -27,4 +27,12 @@
     t.column :red, :integer
     t.column :black, :integer
   end
+
+  create_table :things, :force => true do |t|
+    t.column :body, :text
+    t.column :parent_id, :integer
+    t.column :lft, :integer
+    t.column :rgt, :integer
+    t.column :children_count, :integer
+  end
 end

spec/fixtures/things.yml

@@ -0,0 +1,27 @@
+parent1:
+  id: 1
+  body: Top Level
+  lft: 1
+  rgt: 10
+  children_count: 2
+child_1:
+  id: 2
+  body: Child 1
+  parent_id: 1
+  lft: 2
+  rgt: 3
+  children_count: 0
+child_2:
+  id: 3
+  body: Child 2
+  parent_id: 1
+  lft: 4
+  rgt: 7
+  children_count: 0
+child_2_1:
+  id: 4
+  body: Child 2.1
+  parent_id: 3
+  lft: 8
+  rgt: 9
+  children_count: 0

spec/support/models.rb

@@ -40,4 +40,8 @@ def recurse &block
       end
     }
   end
+end
+
+class Thing < ActiveRecord::Base
+  acts_as_nested_set :counter_cache => 'children_count'
 end