# multicast

#### signature: `multicast(selector: Function): Observable`

## Share source utilizing the provided Subject.

### Examples

**Example 1: multicast with standard Subject**

( [StackBlitz](https://stackblitz.com/edit/typescript-vge8sk?file=index.ts\&devtoolsheight=100) | [jsBin](http://jsbin.com/zexuyosuvi/1/edit?js,console) | [jsFiddle](https://jsfiddle.net/btroncone/x2z7p1gm/) )

```js
// RxJS v6+
import { Subject, interval } from 'rxjs';
import { take, tap, multicast, mapTo } from 'rxjs/operators';

//emit every 2 seconds, take 5
const source = interval(2000).pipe(take(5));

const example = source.pipe(
  //since we are multicasting below, side effects will be executed once
  tap(() => console.log('Side Effect #1')),
  mapTo('Result!')
);

//subscribe subject to source upon connect()
const multi = example.pipe(multicast(() => new Subject()));
/*
  subscribers will share source
  output:
  "Side Effect #1"
  "Result!"
  "Result!"
  ...
*/
const subscriberOne = multi.subscribe(val => console.log(val));
const subscriberTwo = multi.subscribe(val => console.log(val));
//subscribe subject to source
multi.connect();
```

**Example 2: multicast with ReplaySubject**

( [StackBlitz](https://stackblitz.com/edit/typescript-n5ghjj?file=index.ts\&devtoolsheight=100) | [jsBin](http://jsbin.com/ruhexuhike/1/edit?js,console) | [jsFiddle](https://jsfiddle.net/btroncone/oj68u58j/) )

```js
// RxJS v6+
import { interval, ReplaySubject } from 'rxjs';
import { take, multicast, tap, mapTo } from 'rxjs/operators';

//emit every 2 seconds, take 5
const source = interval(2000).pipe(take(5));

//example with ReplaySubject
const example = source.pipe(
  //since we are multicasting below, side effects will be executed once
  tap(_ => console.log('Side Effect #2')),
  mapTo('Result Two!')
);
//can use any type of subject
const multi = example.pipe(multicast(() => new ReplaySubject(5)));
//subscribe subject to source
multi.connect();

setTimeout(() => {
  /*
   subscriber will receieve all previous values on subscription because
   of ReplaySubject
   */
  const subscriber = multi.subscribe(val => console.group(val));
}, 5000);
```

### Additional Resources

* [multicast](https://rxjs.dev/api/operators/multicast) 📰 - Official docs

***

> 📁 Source Code: <https://github.com/ReactiveX/rxjs/blob/master/packages/rxjs/src/internal/operators/multicast.ts>