How I can call Observable.complete callback function? It doesn't work - ionic-framework

Question

In ionic 2, (and angularfire2#4.0.0-rc.0, firebase#3.9.0)
I tried this code, but complete function doesn't work!
constructor(public af: AngularFireDatabase, ...) {
this.temp = af.list('/myTest').subscribe(data => {
... // my tastks
}, error => {
console.log(error);
}, () => {
console.log("done!"); // I can't see this output!
});
}
I already tried very many times, but I can't see "done".
In another function, I tried this but the result is same with first.
console.log(this.temp.closed); // false
this.temp.unsubscribe()
console.log(this.temp.closed); // true
,, What can I do..?

Answer 1

AngularFire list and object observables do not complete. Their internal Firebase refs remain connected, listening for changes to the database.
If you want the list to complete after the first value is received, you can use the first operator:
import "rxjs/add/operator/first";
constructor(public af: AngularFireDatabase, ...) {
this.temp = af.list('/myTest')
.first()
.subscribe(data => {
... // my tastks
}, error => {
console.log(error);
}, () => {
console.log("done!");
});
}
Note that complete handlers are not called upon unsubscription. They are called when the observable completes.
If you want a callback to be invoked upon either completion or unsubscription, you can use the finally operator instead:
import "rxjs/add/operator/finally";
constructor(public af: AngularFireDatabase, ...) {
this.temp = af.list('/myTest')
.finally(() => {
console.log("done!");
})
.subscribe(data => {
... // my tastks
}, error => {
console.log(error);
});
}