Add registration_limit to conference model. Added the input for registration limit in the edit conference form. In the controller, if the limit has exceeded redirect to root_path with an alert. fix #761

app/models/conference.rb

@@ -65,6 +65,7 @@ class Conference < ActiveRecord::Base
 
   validates_uniqueness_of :short_title
   validates_format_of :short_title, with: /\A[a-zA-Z0-9_-]*\z/
+  validates :registration_limit, numericality: { only_integer: true, greater_than_or_equal_to: 0 }
 
   # This validation is needed since a conference with a start date greater than the end date is not possible
   validate :valid_date_range?
@@ -536,6 +537,10 @@ class Conference < ActiveRecord::Base
     email_settings.conference_registration_dates_updated_body
   end
 
+  def registration_limit_exceeded?
+    registration_limit > 0 && registrations.count >= registration_limit
+  end
+
   private
 
   after_create do

app/models/registration.rb

@@ -26,6 +26,7 @@ class Registration < ActiveRecord::Base
   validates :user, presence: true
 
   validates_uniqueness_of :user_id, scope: :conference_id, message: 'already Registered!'
+  validate :registration_limit_not_exceed, on: :create
 
   after_create :set_week, :subscribe_to_conference, :send_registration_mail
 
@@ -49,4 +50,10 @@ class Registration < ActiveRecord::Base
     self.week = created_at.strftime('%W')
     save!
   end
+
+  def registration_limit_not_exceed
+    if self.conference.registration_limit>0 && self.conference.registrations(:reload).count >= self.conference.registration_limit
+      errors.add(:base, 'Registration limit exceeded')
+    end
+  end
 end