The
Join
operator combines the items emitted by two Observables, and selects which items to
combine based on duration-windows that you define on a per-item basis. You implement these windows as
Observables whose lifespans begin with each item emitted by either Observable. When such a window-defining
Observable either emits an item or completes, the window for the item it is associated with closes. So long as
an item’s window is open, it will combine with any item emitted by the other Observable. You define the
function by which the items combine.
Most ReactiveX implementations that have a
Join
operator also have a
GroupJoin
operator that is similar, except that the function you define to combine items emitted by the two Observables
pairs individual items emitted by the source Observable not with an item from the second Observable, but with
an Observable that emits items from the second Observable that fall in the same window.
See Also
CombineLatest
Introduction to Rx
: Join
Introduction to Rx
: GroupJoin
101 Rx Samples
: GroupJoin — Joins two streams by matching by one of their attributes
Language-Specific Information:
the second Observable to combine with the source Observable
a function that accepts an item from the source Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the second Observable
a function that accepts an item from the second Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the first Observable
a function that accepts an item from the first Observable and an item from the second Observable and returns an item to be emitted by the Observable returned from
join
join
does not by default operate on any particular
Scheduler
.
Javadoc:
Join(Observable,Func1,Func1,Func2)
the second Observable to combine with the source Observable
a function that accepts an item from the source Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the second Observable
a function that accepts an item from the second Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the first Observable
a function that accepts an item from the first Observable and an Observable that emits items from the second Observable and returns an item to be emitted by the Observable returned from
groupJoin
groupJoin
does not by default operate on any particular
Scheduler
.
Javadoc:
groupJoin(Observable,Func1,Func1,Func2)
Note that there is also a
join
operator in the optional
StringObservable
class.
It converts an Observable that emits a sequence of strings into an Observable that emits a single string
that concatenates them all, separating them by a specified string delimiter.
the second Observable to combine with the source Observable
a function that accepts an item from the source Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the second Observable
a function that accepts an item from the second Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the first Observable
a function that accepts an item from the first Observable and an item from the second Observable and returns an item to be emitted by the Observable returned from
join
join
does not by default operate on any particular
Scheduler
.
Javadoc:
Join(Observable,Func1,Func1,Func2)
the second Observable to combine with the source Observable
a function that accepts an item from the source Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the second Observable
a function that accepts an item from the second Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the first Observable
a function that accepts an item from the first Observable and an Observable that emits items from the second Observable and returns an item to be emitted by the Observable returned from
groupJoin
groupJoin
does not by default operate on any particular
Scheduler
.
Javadoc:
groupJoin(Observable,Func1,Func1,Func2)
Note that there is also a
join
operator in the optional
StringObservable
class.
It converts an Observable that emits a sequence of strings into an Observable that emits a single string
that concatenates them all, separating them by a specified string delimiter.
the second Observable to combine with the source Observable
a function that accepts an item from the source Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the second Observable
a function that accepts an item from the second Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the first Observable
a function that accepts an item from the first Observable and an item from the second Observable and returns an item to be emitted by the Observable returned from
join
Sample Code
var xs = Rx.Observable.interval(100)
.map(function (x) { return 'first' + x; });
var ys = Rx.Observable.interval(100)
.map(function (x) { return 'second' + x; });
var source = xs
.join(
function () { return Rx.Observable.timer(0); },
function () { return Rx.Observable.timer(0); },
function (x, y) { return x + y; }
.take(5);
var subscription = source.subscribe(
function (x) { console.log('Next: ' + x); },
function (err) { console.log('Error: ' + err); },
function () { console.log('Completed'); });
Next: first0second0
Next: first1second1
Next: first2second2
Next: first3second3
Next: first4second4
Completed
the second Observable to combine with the source Observable
a function that accepts an item from the source Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the second Observable
a function that accepts an item from the second Observable and returns an Observable whose lifespan governs the duration during which that item will combine with items from the first Observable
a function that accepts an item from the first Observable and an Observable that emits items from the second Observable and returns an item to be emitted by the Observable returned from
groupJoin
Sample Code
ar xs = Rx.Observable.interval(100)
.map(function (x) { return 'first' + x; });
var ys = Rx.Observable.interval(100)
.map(function (x) { return 'second' + x; });
var source = xs.groupJoin(
function () { return Rx.Observable.timer(0); },
function () { return Rx.Observable.timer(0); },
function (x, yy) {
return yy.select(function (y) {
return x + y;
}).mergeAll().take(5);
var subscription = source.subscribe(
function (x) { console.log('Next: ' + x); },
function (err) { console.log('Error: ' + err); },
function () { console.log('Completed'); });
Next: first0second0
Next: first1second1
Next: first2second2
Next: first3second3
Next: first4second4
Completed
join
and
groupJoin
are found in each of the following distributions:
rx.all.js
rx.all.compat.js
rx.coincidence.js
ReactiveX
is a collection of open source projects. The content of this
page is licensed under Creative Commons Attribution 3.0 License, and
code samples are licensed under the BSD License.
