Paperclip-Simple-Template.rb

# Inside the model.rb

  has_attached_file :image,
    :url  => "/assets/images/:style/:id.:basename.:extension",
    :path => ":rails_root/public/assets/images/:style/:id.:basename.:extension",
    :styles => {
      :small => '50x45#',
      :medium => '150x150',
      :large => '300x300'
    }
    
  # Validations
  validates_attachment_presence     :image, :message      => "You are required to select an image."
  validates_attachment_size         :image, :less_than    => 2.megabytes, :message => "must be less than 500 kilobytes."
  validates_attachment_content_type :image, :content_type => ['image/jpg', 'image/jpeg','image/gif','image/png','image/pjpeg','image/x-png'], :message => "Must be JPG PNG or GIF."