I'm trying to figure out an rxjs way of doing the following:
You have two observables, one onAddObs and onRemoveObs. let's say onAddObs.next() fires a few times, adding "A", "B", "C". I would like to then get ["A", "B", "C"].
.toArray requires the observable be completed...yet more could come.
That's the first part. The second part is probably obvious... I want onRemoveObs to then remove from the final resulting array.
I don't have a plunkr cuz I can't get anything close to doing this... Thanks in advance!
UPDATE
Based on user3743222's advice, I checked out .scan, which did the job! If anyone else has trouble with this, I've included an angular2 service which shows a nice way of doing this. The trick is to use .scan and instead of streams of what was added/removed, have streams of functions to add/remove, so you can call them from scan and pass the state.
@Injectable()
export class MyService {
public items: Observable<any>;
private operationStream: Subject<any>;
constructor() {
this.operationStream = Subject.create();
this.items = this.operationStream
// This may look strange, but if you don't start with a function, scan will not run....so we seed it with an operation that does nothing.
.startWith(items => items)
// For every operation that comes down the line, invoke it and pass it the state, and get the new state.
.scan((state, operation:Function) => operation(state), [])
.publishReplay(1).refCount();
this.items.subscribe(x => {
console.log('ITEMS CHANGED TO:', x);
})
}
public add(itemToAdd) {
// create a function which takes state as param, returns new state with itemToAdd appended
let fn = items => items.concat(itemToAdd);
this.operationStream.next(fn);
}
public remove(itemToRemove) {
// create a function which takes state as param, returns new array with itemToRemove filtered out
let fn = items => items.filter(item => item !== itemToRemove);
this.operationStream.next(fn);
}
}
