Angular Observables provide the support for passing the messages between publishers(Creator of Observables) and subscribers(User of Observables) in your application. Observables are declarative that is, you define the function for publishing values, but it is not executed until the consumer subscribes to it. We have already covered the  Angular 9 Tutorial on this blog.

The observable can deliver the multiple values of any type like literals, messages, or events, depending on the context. As a publisher, you can create an Observable instance that defines a subscriber function. This is a function that is executed when the consumer calls the subscribe() method.

Define Angular Observers

The handler for receiving the observable notifications implements the Observer interface. It is an object that defines the callback methods to handle the three types of notifications that an observable can send. These are the following.

1. next: Required. The handler for each delivered value called zero or more times after execution starts.
2. error: Optional. The handler for error notification. The error halts the execution of the observable instance.
3. complete: Optional. The handler for an execution-complete notification. The delayed values can continue to be delivered to a next handler after execution is complete.

#angular #angular observables #angular 9