If you're using getValue() you're doing something imperative in declarative paradigm. We try to use BehaviorSubject to share API data across multiple components. We can also pass the initial value to the Behavior Subject when we define it. Ben Lesh. Imagine subscribing to a magazine, and right away you receive the latest published issue of it. It only emits the last value of the source Observable(and only the last value) only after that source Observable completes. BehaviorSubject: Get last message. initialValue (Any): Initial value sent to observers when no other value has been received by the subject yet. Subject in Angular 8 . And yet BehaviorSubject.last() only returns an Observable, and it doesn't seem to expose any methods of T return type. Copy link Contributor paulpdaniels commented Apr 21, 2017. BehaviorSubject represents a value that changes over time, like the user authentication status. And whenever a new Observer subscribes, it immediately receives the stored last value from the BehaviorSubject.There represents a value that changes over time. A BehaviorSubject emits its last emitted value to new/late subscribers; It has an initial value; Its current value can be accessed via the getValue method; A new value can be emitted using the next method; A BehaviorSubject is multicast: Internally it holds a list of all subscribers. BehaviorSubject (value) ¶ Represents a value that changes over time. As BehaviorSubject, ReplaySubject can also replays the last value that was sent out to any new subscribers. When you subscribe to a behavior subject, it will give you the last emitted value right away. By using behaviorsubject I am able to get the last emitted value in same component, but after navigating to another component I get the default value (NOT the last emitted value) It also has a method getValue() to get the current value When a value is emitted, it is passed to subscribers and the Observable is done with it. Angular RxJs: Get last value from anyControl.valueChanges- similar to BehaviorSubject. The only way you should be getting values "out of" an Observable/Subject is with subscribe! On my component I am triggering a HTTP request and updating the subject once the response is returned. The problem starts when I get the control value as @Input, and initialize it in ngOnChanges. AsyncSubject An AsyncSubject emits the last value (and only the last value) emitted by the source Observable, and only after that source Observable completes. But subject doesn’t return the current value on Subscription. BehaviorSubject is a special type of Subject whose only different is that it will emit the last value upon a new observer's subscription. I'm trying to get the current value of a BehaviorSubject without subscribing to it because I need to make some changes afterwards, without the changes reflecting real-time because of a specific requirement. The BehaviorSubject has the characteristic that it stores the “current” value. This type of Subject keeps the last value emitted to the data consumer, and if we will subscribe to new Observer to the Behavior Subject, it will receive that value immediately. But the real power of the BehaviorSubject, in this case, is that every subscriber will always get the initial or the last value that the subject emits. I guess I could also create a throw-away subscription in my getter, only to obtain the latest value with it and then return it to the calling code, but this seems clunky. 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