Improving check-in process

mark user as present for the conference when user's registration ticket for that conference is scanned

app/models/user.rb

@@ -47,7 +47,11 @@ class User < ActiveRecord::Base
   has_many :event_users, dependent: :destroy
   has_many :events, -> { uniq }, through: :event_users
   has_many :presented_events, -> { joins(:event_users).where(event_users: {event_role: 'speaker'}).uniq }, through: :event_users, source: :event
-  has_many :registrations, dependent: :destroy
+  has_many :registrations, dependent: :destroy do
+    def for_conference conference
+      where(conference: conference).first
+    end
+  end
   has_many :events_registrations, through: :registrations
   has_many :ticket_purchases, dependent: :destroy
   has_many :payments, dependent: :destroy
@@ -93,6 +97,12 @@ class User < ActiveRecord::Base
     event_registration.attended
   end
 
+  def mark_attendance_for_conference conference
+    registration = registrations.for_conference(conference)
+    registration.attended = true
+    registration.save
+  end
+
   def name
     self[:name].blank? ? username : self[:name]
   end