Increases/decreases custom counters when taggings are created/destroyed

config/initializers/acts_as_taggable_on.rb

@@ -1,8 +1,24 @@
 ActsAsTaggableOn::Tagging.class_eval do
-  after_destroy :touch_taggable
+  after_create :increase_custom_counter
+  after_destroy :touch_taggable, :decrease_custom_counter
 
   def touch_taggable
     taggable.touch if taggable.present?
   end
 
-end
+  def increase_custom_counter
+    ActsAsTaggableOn::Tag.increment_counter(custom_counter_field_name, tag_id)
+  end
+
+  def decrease_custom_counter
+    ActsAsTaggableOn::Tag.decrement_counter(custom_counter_field_name, tag_id)
+  end
+
+  private
+
+  def custom_counter_field_name
+    "#{self.taggable_type.underscore.pluralize}_count"
+  end
+
+
+end

spec/lib/acts_as_taggable_on_spec.rb

@@ -0,0 +1,47 @@
+require 'rails_helper'
+
+describe 'ActsAsTaggableOn::Tagging' do
+
+  describe "when tagging debates or proposals" do
+    let(:proposal) { create(:proposal) }
+    let(:debate) { create(:debate) }
+
+    it "increases and decreases the tag's custom counters" do
+      tag = ActsAsTaggableOn::Tag.create(name: "foo")
+
+      expect(tag.debates_count).to eq(0)
+      expect(tag.proposals_count).to eq(0)
+
+      proposal.tag_list.add("foo")
+      proposal.save
+      tag.reload
+
+      expect(tag.debates_count).to eq(0)
+      expect(tag.proposals_count).to eq(1)
+
+      debate.tag_list.add("foo")
+      debate.save
+      tag.reload
+
+      expect(tag.debates_count).to eq(1)
+      expect(tag.proposals_count).to eq(1)
+
+      proposal.tag_list.remove("foo")
+      proposal.save
+      tag.reload
+
+      expect(tag.debates_count).to eq(1)
+      expect(tag.proposals_count).to eq(0)
+
+      debate.tag_list.remove("foo")
+      debate.save
+      tag.reload
+
+      expect(tag.debates_count).to eq(0)
+      expect(tag.proposals_count).to eq(0)
+    end
+
+  end
+
+
+end