


A brief analysis of observable objects, observers and RxJS operators in Angular
This article will introduce you to the observable objects (Observable), observers (observer) and RxJS operators in Angular. I hope it will be helpful to everyone!
Observable (observable object)
Observable
(observable object) is inside the RxJS
library An object that can be used to handle asynchronous events, such as HTTP requests (in fact, in Angular, all HTTP requests return Observable). [Recommended tutorials: "angular tutorial"]
Perhaps, you have come into contact with something called promise
before. They are essentially the same: they are all produced The operator actively "push" products to consumers, while consumers passively receive them, but there is still a big difference between them: Observable
can send any number of values, and, after being subscribed Before, it would not execute ! This is a feature that promise
does not have.
-
Observable
is used to transmit messages between the sender and the receiver. You can regard these messages as streams - When creating
Observable
object, you need to pass in a function as a parameter of the constructor. This function is called Subscriber function . This function is where the producer pushes messages to the consumer. - Before being
subscribe
(subscribed) by the consumer, the subscriber function will not be executed until thesubscribe()
function is called, which returns asubscription
object, There is aunsubscribe()
function inside, and consumers can refuse to receive messages at any time! -
subscribe()
The function receives anobserver(observer)
object as an input parameter - The sending of the message can be synchronous or Asynchronous
observer (observer)
With an observable object (sender)
, you need an observer (receiver)
To observe observable objects, the observer must implement the observer
interface, which is an object containing three properties, all of which are functions, as follows:
Notification Type | Description |
---|---|
Required. Use the received value as input parameter and execute under normal circumstances. May be executed zero or more times. | |
Optional. Executed in case of error. Errors interrupt the execution of this observable object instance. | |
Optional. Executed when the transfer is completed. |
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