Basic validation on sections

app/models/alert.rb

@@ -22,6 +22,8 @@ class Alert < ActiveRecord::Base
   validates :semester,    :presence     => true
 
   serialize :sections, Array
+  validate :section_check
+  
 
   scope :user_alerts, lambda { |user_id| 
     where('Alerts.user_id = ?', user_id)
@@ -34,4 +36,20 @@ class Alert < ActiveRecord::Base
   def course_name
     "#{self.department} #{self.course}"
   end
+
+  protected 
+    def section_check
+      section_count = 0
+      sections.each do |section|
+        unless section =~ /^[A-Za-z0-9 ]$/ || section.empty?
+          errors.add(:sections, 'You entered an invalid section number')
+        else
+          section_count += 1 if !section.empty?
+        end
+      end
+
+      if section_count == 0
+        errors.add(:sections, 'You must enter at least one section')
+      end
+    end
 end