asynchronous - Angular *ngFor bound to observable with async pipe - whats happening? -

i have started angular4 , have came against conceptual problem. async pipe (used in combination *ngfor in case) meant subscribe observable , away manual subscriptions. looking @ examples on web:

case 1: binding observable contains single items such observable<user>

case 2: binding observable contains arrays of items such observable<user[]>

case 3: variations of 1 , 2 subject, promise or behavioursubject

(example of case 1 single item: http://briantroncone.com/?p=623)

(example of case 2 array: http://www.concretepage.com/angular-2/angular-2-async-pipe-example)

conceptually ngfor iterates on enumerable , i'm assuming enumerable item emitted observable , not observable itself.

so *ngfor="let user of users" going work on observable<user[]> , not observable<user>?

the *ngfor triggered each item arrives observable?

if case how can bind observable of item , not item[], how ngfor iterate on item when not enumerable? thanks.

*ngfor="let user of users" going work on observable<user[]> , not observable<user>?

yes, ngfor directive create template once per item iterable. see description of ngfor. iterable not object.

the *ngfor triggered each item arrives observable?

no, while using observable, ngfor work when observable emit value(entire iterable not pre item of it).

how ngfor iterate on item when not enumerable?

since ngfor supports iterable, can create pipe converting object array object.values or object.keys ngfor can iterate.