Rxjs Promise as observable
I would like to find a receipt to receive Promise
, for example Observable
I mean: which Observable
provides one value and completes,
and any caller (before and after completion) should receive that single value.
I came out with a combination of Rx.Observable.create
publishLast
and connect
.
var getPromiseLike=function(){
console.log('getPromiseLike()');
//// var an_object={}; <--- this should happen inside Obs function
var prom_like = Rx.Observable.create(function(obs) {
var an_object={}; /// <--- here !
setTimeout(function(){
obs.onNext(an_object);
obs.onCompleted();
},500);
}).publishLast();
prom_like.connect();
return prom_like;
};
var promiselike=getPromiseLike();
var obj1;
promiselike
.subscribe(function(obj){
console.log('onNext1');
obj1 = obj;
},
function(err){},
function(){
console.log('onComplete1');
});
setTimeout(function(){
promiselike
.subscribe(function(obj){
console.log('onNext2 obj1===obj :'+(obj1===obj)); //true
},
function(err){},
function(){
console.log('onComplete2');
});
},1000);
/*LOGS:
getPromiseLike()
script.js:19 onNext1
script.js:24 onComplete1
script.js:31 onNext2 obj1===obj :true
script.js:35 onComplete2
*/
Is this the simplest solution, or are there some built-in ones I missed? plnkr
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In RxJS, usually both are modeled as a construct AsyncSubject
.
It has many properties that promises have and are useful:
- It only gets one value, like a promise, and will call the next one with that value only.
- It caches this value for all future calculations.
- This is a topic, so it is similar to the one deferred in some promise libraries.
Note: Personally, I don't see a problem mixing promises with observables, I am doing it in my own code and Rx plays with promises nicely.
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