Angular JS指令的return语句中的'^^'是什么意思

Question

I have seen the following code somewhere in my code but i am not able to find any help on google or anywhere.

    app.directive('widget', [function () {
    return {
        require: '^^dashboard',

There you can see '^^' symbol used in required attribute. I need to understand the purpose.

Answer 1

From the docs :

The myPane directive has a require option with value ^^myTabs. When a directive uses this option, $compile will throw an error unless the specified controller is found. The ^^ prefix means that this directive searches for the controller on its parents. (A ^ prefix would make the directive look for the controller on its own element or its parents; without any prefix, the directive would look on its own element only.)