Modellazione RxJS in caso contrario strutture di controllo con operatori Observables

Question

E 'possibile modellare se/o strutture di controllo tramite operatori RxJS. Per quanto ho capito, è possibile utilizzare Observable.filter() per simulare un ramo IF, ma non sono sicuro di simulare un ramo ELSE tramite uno degli operatori Observable.

Answer 1

ci sono un paio operatori che si potrebbe usare per emulare questo:

In ordine da molto probabilmente quello che stai chiedendo fo

partition

//Returns an array containing two Observables 
//One whose elements pass the filter, and another whose elements don't 

var items = observableSource.partition((x) => x % 2 == 0); 

var evens = items[0]; 
var odds = items[1]; 

//Only even numbers 
evens.subscribe(); 

//Only odd numbers 
odds.subscribe(); 

groupBy

//Uses a key selector and equality comparer to generate an Observable of GroupedObservables 
observableSource.groupBy((value) => value % 2, (value) => value) 
    .subscribe(groupedObservable => { 
    groupedObservable.subscribe(groupedObservable.key ? oddObserver : evenObserver); 
    }); 

if

//Propagates one of the sources based on a particular condition 
//!!Only one Observable will be subscribed to!! 
Rx.Observable.if(() => value > 5, Rx.Observable.just(5), Rx.Observable.from([1,2, 3])) 

case (disponibile solo in RxJS 4)

//Similar to `if` but it takes an object and only propagates based on key matching 
//It takes an optional argument if none of the items match 
//!!Only one Observable will be subscribed to!! 
Rx.Observable.case(() => "blah", 
{ 
    blah : //..Observable, 
    foo : //..Another Observable, 
    bar : //..Yet another 
}, Rx.Observable.throw("Should have matched!"))