'Require' in Angular Directives with '^^'

Question

There is the following code:

ff.directive('radarMapMap', {
  restrict: 'A',
  require: '^^radarMap',
  link: function (scope, element, attrs, mapCtrl) {
    mapCtrl.setMapElement(element);
  }
});

I don't understand what is the difference between require: '^radarMap' and require: '^^radarMap'. I didn't find it in documentation. Please, make me clear. Thanks in advance!

Answer 1

from the documentation:

^ - Locate the required controller by searching the element and its parents. Throw an error if not found.

^^ - Locate the required controller by searching the element's parents. Throw an error if not found.

Read it here: https://docs.angularjs.org/api/ng/service/$compile