fix revision count and drop observers

Gemfile

@@ -22,9 +22,6 @@ gem 'responders', '~> 2.0'
 gem 'mysql2'
 # gem 'pg'
 
-# for observing records
-gem 'rails-observers'
-
 # for tracking data changes
 gem 'paper_trail'
 

Gemfile.lock

@@ -399,8 +399,6 @@ GEM
     rails-i18n (4.0.8)
       i18n (~> 0.7)
       railties (~> 4.0)
-    rails-observers (0.1.2)
-      activemodel (~> 4.0)
     rails_12factor (0.0.3)
       rails_serve_static_assets
       rails_stdout_logging
@@ -632,7 +630,6 @@ DEPENDENCIES
   rails-assets-trianglify!
   rails-assets-waypoints!
   rails-i18n (~> 4.0.0)
-  rails-observers
   rails_12factor
   rdoc-generator-fivefish
   redcarpet

app/models/concerns/revision_count.rb

@@ -0,0 +1,11 @@
+module RevisionCount
+  extend ActiveSupport::Concern
+
+  included do
+    after_update :increment_revision
+  end
+
+  def increment_revision
+    conference.update_column(:revision, conference.revision + 1)
+  end
+end

app/models/conference.rb

@@ -1,4 +1,5 @@
 class Conference < ActiveRecord::Base
+  include RevisionCount
   require 'uri'
   serialize :events_per_week, Hash
   # Needed to call 'Conference.with_role' in /models/ability.rb
@@ -734,6 +735,15 @@ class Conference < ActiveRecord::Base
     (start_hour..(end_hour - 1)).cover?(current_hour) ? current_hour - start_hour : 0
   end
 
+  ##
+  # Return the current conference object to be used in RevisionCount
+  #
+  # ====Returns
+  # * +ActiveRecord+
+  def conference
+    self
+  end
+
   private
 
   # Returns a different html colour for every i and consecutive colors are

app/models/event.rb

@@ -1,5 +1,6 @@
 class Event < ActiveRecord::Base
   include ActiveRecord::Transitions
+  include RevisionCount
   has_paper_trail on: [:create, :update], ignore: [:updated_at, :guid, :week], meta: { conference_id: :conference_id }
 
   acts_as_commentable
@@ -251,6 +252,10 @@ class Event < ActiveRecord::Base
     event_schedules.find_by(schedule_id: program.selected_schedule_id).try(:start_time)
   end
 
+  def conference
+    program.conference
+  end
+
   private
 
   ##

app/models/revision_observer.rb

@@ -1,26 +0,0 @@
-#
-# suseconferenceclient relies on a 'revision' attribute for caching and
-# doing some calculations.
-#
-# It should be incremented after any change in the conference or in any
-# associated models
-#
-# This observer updates the revision column in a non-intrusive way,
-# preventing validations, callbacks or exceptions to be triggered
-#
-# Relying on paper_trail could also be an option, but a 'revision' column
-# in table 'conferences' looks like a more simple and straightforward solution
-#
-class RevisionObserver < ActiveRecord::Observer
-  observe :conference, :event, :room, :track
-
-  def after_save(model)
-    begin
-      conference = model.kind_of?(Conference) ? model : model.conference
-      conference.reload.increment(:revision)
-      conference.update_column(:revision, conference.revision)
-    rescue
-      nil
-    end
-  end
-end

app/models/room.rb

@@ -1,4 +1,5 @@
 class Room < ActiveRecord::Base
+  include RevisionCount
   belongs_to :venue
   has_many :event_schedules, dependent: :destroy
 
@@ -10,6 +11,10 @@ class Room < ActiveRecord::Base
 
   validates :size, numericality: { only_integer: true, greater_than: 0 }, allow_nil: true
 
+  def conference
+    venue.conference
+  end
+
   private
 
   def generate_guid

app/models/track.rb

@@ -1,4 +1,5 @@
 class Track < ActiveRecord::Base
+  include RevisionCount
   belongs_to :program
   has_many :events, dependent: :nullify
 
@@ -16,6 +17,10 @@ class Track < ActiveRecord::Base
 
   before_validation :capitalize_color
 
+  def conference
+    program.conference
+  end
+
   private
 
   def generate_guid

config/application.rb

@@ -25,7 +25,6 @@ module Osem
 
     # Activate observers that should always be running.
     # config.active_record.observers = :cacher, :garbage_collector, :forum_observer
-    config.active_record.observers = :revision_observer
 
     # Set Time.zone default to the specified zone and make Active Record auto-convert to this zone.
     # Run "rake -D time" for a list of tasks for finding time zone names. Default is UTC.

db/migrate/20170108053041_add_default_to_revision_in_conference.rb

@@ -0,0 +1,5 @@
+class AddDefaultToRevisionInConference < ActiveRecord::Migration
+  def change
+    change_column :conferences, :revision, :integer, default: 0, null: false
+  end
+end

db/schema.rb

@@ -90,7 +90,7 @@ ActiveRecord::Schema.define(version: 20170629232817) do
     t.datetime "created_at"
     t.datetime "updated_at"
     t.string   "logo_file_name"
-    t.integer  "revision"
+    t.integer  "revision",           default: 0,     null: false
     t.boolean  "use_vpositions",     default: false
     t.boolean  "use_vdays",          default: false
     t.boolean  "use_volunteers"

spec/models/conference_spec.rb

@@ -1660,4 +1660,31 @@ describe Conference do
       expect{ conference.save }.to change{ EventSchedule.count }.from(2).to(1)
     end
   end
+
+  describe '#revision' do
+    let(:track) { create(:track, program: subject.program) }
+    let(:event) { create(:event, program: subject.program, track: track) }
+    let(:venue) { create(:venue, conference: subject) }
+    let(:room)  { create(:room, venue: venue) }
+
+    it 'for change in conference' do
+      subject.title = 'changed'
+      expect{ subject.save }.to change { subject.revision }.by(1)
+    end
+
+    it 'for change in event' do
+      event.title = 'changed'
+      expect{ event.save }.to change { subject.revision }.by(1)
+    end
+
+    it 'for change in track' do
+      track.name = 'changed'
+      expect{ track.save }.to change { subject.revision }.by(1)
+    end
+
+    it 'for change in room' do
+      room.name = 'changed'
+      expect{ room.save }.to change { subject.revision }.by(1)
+    end
+  end
 end