A Subject is a special type of Observable that allows values to be multicasted to many Observers. Subjects are like EventEmitters.

class Subject<T> extends Observable implements SubscriptionLike {
  static create: Function
  constructor()
  observers: Observer<T>[]
  closed: false
  isStopped: false
  hasError: false
  thrownError: any
  lift<R>(operator: Operator<T, R>): Observable<R>
  next(value?: T)
  error(err: any)
  complete()
  unsubscribe()
  _trySubscribe(subscriber: Subscriber<T>): TeardownLogic
  _subscribe(subscriber: Subscriber<T>): Subscription
  asObservable(): Observable<T>

  // inherited from index/Observable
  static create: Function
  static if: typeof iif
  static throw: typeof throwError
  constructor(subscribe?: (this: Observable<T>, subscriber: Subscriber<T>) => TeardownLogic)
  _isScalar: boolean
  source: Observable<any>
  operator: Operator<any, T>
  lift<R>(operator: Operator<T, R>): Observable<R>
  subscribe(observerOrNext?: PartialObserver<T> | ((value: T) => void), error?: (error: any) => void, complete?: () => void): Subscription
  _trySubscribe(sink: Subscriber<T>): TeardownLogic
  forEach(next: (value: T) => void, promiseCtor?: PromiseConstructorLike): Promise<void>
  pipe(...operations: OperatorFunction<any, any>[]): Observable<any>
  toPromise(promiseCtor?: PromiseConstructorLike): Promise<T>
}

Description

Every Subject is an Observable and an Observer. You can subscribe to a Subject, and you can call next to feed values as well as error and complete.

Static Properties

Property	Type	Description
create	Function

Constructor

constructor()

Parameters

There are no parameters.

Properties

Property	Type	Description
observers	Observer<T>[]
closed	false
isStopped	false
hasError	false
thrownError	any

Methods

lift<R>(operator: Operator<T, R>): Observable<R>

Parameters

operator

Type: Operator.

Returns

Observable<R>

next(value?: T)

Parameters

value

Optional. Default is undefined. Type: T.

error(err: any)

Parameters

err	Type: any.

complete()

Parameters

There are no parameters.

unsubscribe()

Parameters

There are no parameters.

_trySubscribe(subscriber: Subscriber<T>): TeardownLogic

Parameters

subscriber

Type: Subscriber.

Returns

TeardownLogic

_subscribe(subscriber: Subscriber<T>): Subscription

Parameters

subscriber

Type: Subscriber.

Returns

Subscription

asObservable(): Observable<T>

Creates a new Observable with this Subject as the source. You can do this to create customize Observer-side logic of the Subject and conceal it from code that uses the Observable.

Parameters

There are no parameters.

Returns

Observable<T>: Observable that the Subject casts to