app/models/attachment.rb
class Attachment < ActiveRecord::Base
belongs_to :case
belongs_to :clinician
has_attached_file :document, styles: { large: "600x600>", medium: "350x350>", small: "200x250>", thumb: ["100x150#", :jpg]}, default_url: "/documents/:style/missing.png"
# validates_attachment_content_type :avatar, content_type: /\Aimage\/.*\Z/
do_not_validate_attachment_file_type :document
end