require – Require another controller be passed into current directive
linking function. The require takes a name of the directive controller
to pass in. If no such controller can be found an error is raised. The name can be prefixed with:

• ? – Don’t raise an error. This makes the require dependency optional.
• ^ – Look for the controller on parent elements as well.

以上是官方文档的定义。这里的歧义是什么是“指令控制器”。

以tabs directive from the angularjs-ui bootstrap project为例。

angular.module('ui.bootstrap.tabs',[])
.controller('TabsController',['$scope','$element',function($scope,$element) {
  ... // omitted for simplicity
}])
.directive('tabs',function() {
  return {
    restrict: 'EA',transclude: true,scope: {},controller: 'TabsController',templateUrl: 'template/tabs/tabs.html',replace: true
  };
})
.directive('pane',['$parse',function($parse) {
  return {
    require: '^tabs',restrict: 'EA',scope:{
      heading:'@'
    },link: function(scope,element,attrs,tabsCtrl) {
      ... // omitted for simplicity
    },templateUrl: 'template/tabs/pane.html',replace: true
  };
}]);

pane指令需要：’^ tabs’，其中tabs是其父元素上的指令的名称，而附加到该指令的控制器的名称是TabsController。从我自己的解释上面的定义，它应该已经要求：’^ TabsController’不需要：’^ tabs’，这显然是错误。请告诉我在我的理解中我错过了什么。