Preview now can be use at both ad_banner and ad_image,however it won't run correctly if user change its ad_banner at ad_image.

app/models/ad_banner.rb

@@ -9,6 +9,7 @@ class AdBanner
 
   before_save :save_or_destroy
   validates_uniqueness_of :title
+  validates :title , :length => { :minimum => 2 }
   has_many :ad_images , dependent: :delete
   
   FX_TYPES = ["blindX","blindY","blindZ","cover","curtainX","curtainY","fade","fadeZoom","growX","growY","scrollUp","scrollDown","scrollLeft","scrollRight","scrollHorz","scrollVert","shuffle","slideX","slideY","toss","turnUp","turnDown","turnLeft","turnRight","uncover","wipe","zoom"]