hao wang thinks this is interesting: The require property is used to inject another directive controller as the fourth parameter of the link function. It means that using this property, we are able to communicate with the other directives. From Creating our own directives from AngularJS Essentials by Rodrigo Branas Publisher: Packt Publishing Released: August 2014 Note Require 属性用于注入其它的指令在 link 方法的第四个参数上。意思就是，使用这个属性，我们可以与其它的指定交流。 Share this highlight http://www.safaribooksonline.com/a/angularjs-essentials/30938/ Twitter Facebook Google Plus Email Get Instant Access Now Start a Free Trial Have an account? Sign in. Minimise Unlock the rest of AngularJS Essentials and 30,000 other books and videos By clicking this box, you confirm that you have read and agree to the terms and conditions of our Membership Agreement, and you understand that when your trial period ends, you will be required to provide billing information if you wish to continue using the service. Unlock the rest of this book Start a Free 10-Day Trial loading Learn about Safari for Business Have an account? Sign in.