Make sure the event type belongs to the parent conference

app/models/event.rb

@@ -22,11 +22,12 @@ class Event < ActiveRecord::Base
   validates :description, presence: true
   validates :agreement, acceptance: true
   validates :track, presence: true
-  validate :track_belongs_to_the_selected_conference
   validates :language, inclusion: {in: I18n.available_locales.map(&:to_s)}, presence: true
   validates :event_type, presence: true
   validates :length, presence: true, numericality: {only_integer: true}
   validate :length_is_within_the_permitted_interval
+  validate :track_belongs_to_the_selected_conference
+  validate :event_type_belongs_to_the_selected_conference
 
   delegate :status, to: :proposition
 
@@ -76,6 +77,12 @@ class Event < ActiveRecord::Base
 
   private
 
+  def event_type_belongs_to_the_selected_conference
+    unless conference.present? and conference.event_types.include?(event_type)
+      errors.add :event_type, :must_be_a_valid_event_type
+    end
+  end
+
   def track_belongs_to_the_selected_conference
     unless conference.present? and conference.tracks.include?(track)
       errors.add :track, :must_be_a_valid_track
@@ -83,8 +90,10 @@ class Event < ActiveRecord::Base
   end
 
   def length_is_within_the_permitted_interval
-    unless length >= event_type.minimum_length and length <= event_type.maximum_length
-      errors.add :length, :must_be_between, minimum: event_type.minimum_length, maximum: event_type.maximum_length
+    if event_type.present?
+      unless length >= event_type.minimum_length and length <= event_type.maximum_length
+        errors.add :length, :must_be_between, minimum: event_type.minimum_length, maximum: event_type.maximum_length
+      end
     end
   end
 end

app/views/management/events/edit.html.slim

@@ -1,5 +1,5 @@
 - content_for :title
-  = t('.edit', event_type: @event.event_type.name.mb_chars.downcase, event_title: @event.title)
+  = t('.edit', event_type: @event.event_type.try(:name).try(:mb_chars).try(:downcase), event_title: @event.title)
 
 .row
   .col-xs-12
@@ -11,9 +11,9 @@
     = simple_nested_form_for [:management, @conference, @event], wrapper: :horizontal_form, html: { class: 'form-horizontal' } do |f|
       = f.input :title
       = f.input :subtitle
-      = f.association :event_type
+      = f.association :event_type, collection: current_conference.event_types
       = f.association :track, collection: current_conference.tracks.map { |track| [track.name, track.id, {title: track.description}] }
-      = f.input :length, hint: t('simple_form.hints.event.length', type: @event.event_type.name.mb_chars.downcase, min: @event.event_type.minimum_length, max: @event.event_type.maximum_length)
+      = f.input :length
       = f.input :language, collection: locale_collection, include_blank: false
       = f.input :abstract
       = f.input :description