Enable and set focus to text input field with checkbox in Angular JS

I have a Bootstrap 3 prepended text field with a checkbox. I want the field to be disabled until the checkbox is true, and then I want to not only enable it but set focus to it

I used the following code and the enable/disable works great, but not sure how to set the focus...

I will likely write a directive, but I was wondering if there was some very simple way to do it as there was for the disable/enable

<div class="input-group">
    <span class="input-group-addon">
        <input type="checkbox" name="cbprepend" ng-model="cbprepend">
    </span>
    <input type="text" id="cbprependfield" class="form-control" ng-disabled="!cbprepend">
</div>

Your approach using a directive is good, but lacks some "angularity".

Here is another possible solution. First, create the directive:

.directive('checkableInput', function() {
return {
    restrict: 'E',
    templateUrl: 'your/template/dir/checkable-input.html',
    scope: {
        id: "@",
        model: "="
    },
    link: function (scope, element, attrs) {
        var input = element.find('#' + scope.id);
        scope.toggleFocus = function() {
            if(scope.model) {
                input.focus();
            } else {
                input.blur();
            }
        }
    }
  };
});

The template specified in templateUrl looks like this:

<div class="input-group">
    <span class="input-group-addon" >
        <input type="checkbox" ng-model="model" ng-change="toggleFocus()">
    </span>
    <input type="text" ng-id="id" class="form-control" ng-enabled="model">
</div>

This is how you use it:

<checkable-input id="cbprependfield" model="cbprepend" />

OK, I did use a Directive, not sure if this is the cleanest way, please give me some criticism...

.directive('pcb', function() {
return {
    restrict: 'A',
    link: function postLink(scope, element, attrs) {
        element.on({
            change: function(e) {
                if (element.is(':checked')) {
                    element.closest('.input-group').find('.focus-target').removeAttr('disabled')
                    element.closest('.input-group').find('.focus-target').focus();
                } else {
                    element.closest('.input-group').find('.focus-target').attr('disabled', 'disabled');
                    element.closest('.input-group').find('.focus-target').blur();
                }
            }
        });
    }
  };
});

with the html

<div class="input-group">
                    <span class="input-group-addon" >
                        <input type="checkbox" pcb ng-model="cbprepend">
                    </span>
                    <input type="text" id="cbprependfield" class="form-control focus-target" disabled>
                </div>