Typescript async/await doesnt update AngularJS view

Question

I'm using Typescript 2.1(developer version) to transpile async/await to ES5.

I've noticed that after I change any property which is bound to view in my async function the view isn't updated with current value, so each time I have to call $scope.$apply() at the end of function.

Example async code:

async testAsync() {
     await this.$timeout(2000);
     this.text = "Changed";
     //$scope.$apply(); <-- would like to omit this
}

And new text value isn't shown in view after this.

Is there any workaround so I don't have to manually call $scope.$apply() every time?

Answer 1

The answers here are correct in that AngularJS does not know about the method so you need to 'tell' Angular about any values that have been updated.

Personally I'd use $q for asynchronous behaviour instead of using await as its "The Angular way".

You can wrap non Angular methods with $q quite easily i.e. [Note this is how I wrap all Google Maps functions as they all follow this pattern of passing in a callback to be notified of completion]

function doAThing()
{
    var defer = $q.defer();
    // Note that this method takes a `parameter` and a callback function
    someMethod(parameter, (someValue) => {
        $q.resolve(someValue)
    });

    return defer.promise;
}

You can then use it like so

this.doAThing().then(someValue => {
    this.memberValue = someValue;
});

However if you do wish to continue with await there is a better way than using $apply, in this case, and that it to use $digest. Like so

async testAsync() {
   await this.$timeout(2000);
   this.text = "Changed";
   $scope.$digest(); <-- This is now much faster :)
}

$scope.$digest is better in this case because $scope.$apply will perform dirty checking (Angulars method for change detection) for all bound values on all scopes, this can be expensive performance wise - especially if you have many bindings. $scope.$digest will, however, only perform checking on bound values within the current $scope making it much more performant.