Update counter cache correctly for STI records (#444)

Fixes #415

CHANGELOG

@@ -1,6 +1,7 @@
 Unreleased version
 
 * Keep current scope when calling `roots` [Petrik de Heus](https://github.com/p8)
+* STI record now can update counter cache correctly [Issei Murasawa](http://github.com/issei-m)
 * [Compare to 3.3.0](https://github.com/collectiveidea/awesome_nested_set/compare/v3.3.1...master)
 
 3.3.1

lib/awesome_nested_set/model.rb

@@ -244,12 +244,12 @@ def update_counter_cache
 
           # Decrease the counter for all old parents
           if old_parent = self.parent
-            self.class.decrement_counter(acts_as_nested_set_options[:counter_cache], old_parent)
+            old_parent.class.decrement_counter(acts_as_nested_set_options[:counter_cache], old_parent)
           end
 
           # Increase the counter for all new parents
           if new_parent = self.reload.parent
-            self.class.increment_counter(acts_as_nested_set_options[:counter_cache], new_parent)
+            new_parent.class.increment_counter(acts_as_nested_set_options[:counter_cache], new_parent)
           end
         end
 

spec/awesome_nested_set_spec.rb

@@ -1104,6 +1104,27 @@ def check_structure(entries, structure)
         expect { subject }.to change { new_parent.reload.children_count }.by(1)
       end
     end
+
+    context "when class is an STI" do
+      let(:sti_subclass1) { Subclass1.create(name: "Subclass1") }
+      let(:sti_subclass2) { Subclass2.create(name: "Subclass2") }
+      let(:sti_subclass3) { Subclass2.create(name: "Subclass3") }
+
+      # https://github.com/collectiveidea/awesome_nested_set/issues/415
+      it 'should update counter cache of a parent' do
+        sti_subclass2.move_to_child_of sti_subclass1
+
+        sti_subclass1.reload
+        expect(sti_subclass1.children_count).to be 1
+
+        sti_subclass2.move_to_child_of sti_subclass3
+
+        sti_subclass1.reload
+        sti_subclass3.reload
+        expect(sti_subclass1.children_count).to be 0
+        expect(sti_subclass3.children_count).to be 1
+      end
+    end
   end
 
   describe "association callbacks on children" do

spec/db/schema.rb

@@ -88,6 +88,7 @@
     t.column :parent_id, :integer
     t.column :lft, :integer
     t.column :rgt, :integer
+    t.column :children_count, :integer, null: false, default: 0
   end
 
   create_table :users, :force => true do |t|

spec/support/models.rb

@@ -155,7 +155,7 @@ class ScopedUser < ActiveRecord::Base
 end
 
 class Superclass < ActiveRecord::Base
-  acts_as_nested_set
+  acts_as_nested_set counter_cache: :children_count
   self.table_name = 'single_table_inheritance'
 end