RxJS pushes current value towards late subscribers
Below is a snippet of HTML that I am using as an example:
<html>
<head>
<script src="rx.all.js"></script>
</head>
<body>
<script>
var source = new Rx.BehaviorSubject(function() {return 2;});
var stuff = source.scan([], function(val, operation) {
return operation(val);
});
stuff.subscribe(function(v) {
console.log("first subscriber");
console.log(v);
});
source.onNext(function(val) {
return val * 2;
});
stuff.subscribe(function(v) {
console.log("second subscriber");
console.log(v);
});
</script>
</body>
Output in JS console:
first subscriber
2
first subscriber
4
second subscriber
0
Now the "stuff" does some processing (mostly by applying a function to the current value), an idea I took from the TodoMVC example for ReactJs + RxJS ( https://github.com/fdecampredon/react-rxjs-todomvc ).
The result I am trying to achieve is that the second subscriber also sees "4" when they subscribe. I am using RxJS in conjunction with ReactJS so the components are unsubscribed when they are unmounted (due to a route change) and subscribed again when they are re-mounted.
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Use replay(1)
to change stuff
to a hot observable that will remember the last value and serve it to later languages:
var stuff = ...;
stuff = stuff.replay(1);
// go ahead and start it listening
// you could use .refCount() here also
var subscription = stuff.connect();
// now subscribe your observers
stuff.subscribe(...);
// send some results
source.onNext(...);
source.onNext(...);
// subscribe another observer
// will see the lastest value
// as well as any new values
stuff.subscribe(...);
source.onNext(...);
// ...
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