upload.rb

class Upload < ActiveRecord::Base
  has_attached_file :document, styles: { thumbnail: "60x60#" }
  validates_attachment :document, content_type: { content_type: ["application/pdf","application/vnd.ms-excel",
             "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
             "application/msword",
             "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
             "text/plain"] }
  validates :name, presence: true
  validates_format_of :email,:with => /\A[^@\s]+@([^@\s]+\.)+[^@\s]+\z/
end