ActiveRecord memo(3)

1. Observer
<br />#可以特別指定, 要觀察誰<br /> class AuditObserver < ActiveRecord::Observer<br /> observe :account, :balance<br /><br /> def after_update(record)<br /> AuditTrail.new(record, "UPDATED")<br /> end<br /> end<br /><br />#然後要在environment 裡設定<br />config.active_record.observers = [:comment_observer, :signup_observer]<br />

2. validate 錯誤時, 可以
<br /> #針對個別屬性errors.add <br /> class User < ActiveRecord::Base<br /> def validate<br /> unless name && name =~ /^\w+$/<br /> errors.add(:name, "is missing or invalid" )<br /> end<br /> end<br /> def validate_on_create<br /> if User.find_by_name(name)<br /> errors.add(:name, "is already being used" )<br /> end<br /> end<br /> end<br /><br /> #針對整個object<br /> def validate<br /> if name.blank? && email.blank?<br /> errors.add_to_base("You must specify a name or an email address" )<br /> end<br /> end<br />