How to properly track data changes in the service?

Question

Angular

Data from the service is used in various directives and controllers, how to track changes correctly? All through watch ?

Answer 1

https://github.com/rubenv/angular-tiny-eventemitter
In services, create methods like onUserChanged that accept a callback and subscribe it to the event.
In controllers do something like

Auth.onUserChanged(function(newUser) {
  vm.user = newUser;
});

Answer 2

You can use eventemitter, or pubsub
The directive, in theory, should not go directly to the service, the controller should go to the service and pass it to the directive (although there are exceptions)