Angular2 fire listen to node changes throws an error

Question

The code below was working and it should listen for changes in a node and execute a function but now am getting an error:

ncaught TypeError: Object(...) is not a function
at SwitchMapSubscriber.eval [as project] (changes.js:7)

So, in my angular2 component I have:

private subscriptions = new Subscription();

registered: AngularFireList<any>;
constructor(private _af: AngularFireDatabase){
     this.registered = _af.list('/registered');
 }

ngOnInit() {
    this.subscriptions.add(
        this.registered.valueChanges().subscribe(
            res => {
                console.log("the value has changed");
            }
        )
    );
}

So where am I going wrong as getting the error above which point to:

angular2fire/database/list/changes

What I need my code to do is to listen to whenever there is a change in a firebase node and log to the console

The subscriptions have also been defined by:

    private subscriptions = new Subscription();

Adding it to the subscriptions then I can use onDestroy lifecycle and prevent memory leaks as shown below

    ngOnDestroy() {
      this.subscriptions.unsubscribe();
    }

Answer 1

This is a popular issue these days. Please upgrade rxjs 5 to version 6.

This happens due to some breaking changes in AngularFire. Once upgraded the function should perform as expected.

Upgrade using: npm install rxjs@6 rxjs-compat@6 --save (Recomended)

Or rollback (Not recomended) using:

npm uninstall angularfire2
npm install [email protected]
npm uninstall firebase
npm install [email protected]

See the rxjs official migration doc for how-to's and more details on the changes between 5 and 6.