@ngdoc error
@name ngRef:noctrl
@fullName A controller for the value of `ngRefRead` could not be found on the element.
@description

This error occurs when the {@link ng.ngRef ngRef directive} specifies
a value in `ngRefRead` that cannot be resolved to a directive / component controller.

Causes for this error can be:

1. Your `ngRefRead` value has a typo.
2. You have a typo in the *registered* directive / component name.
3. The directive / component does not have a controller.

Note that `ngRefRead` takes the name of the component / directive, not the name of controller, and
also not the combination of directive and 'Controller'. For example, for a directive called 'myDirective',
the correct declaration is `<div ng-ref="$ctrl.ref" ng-ref-read="myDirective">`.