Can you explain the concepts of observables, observers, and subscriptions in Angular?

Question

Can you explain the concepts of observables, observers, and subscriptions in Angular?

As I dive into Angular, I find myself tangled in the concepts of observables, observers, and subscriptions. Could you shed some light on these for me?

angular rxjs angular6 rxjs5

Answer 1

Answer №1

Let's take a look at this easy-to-understand visual illustration:

https://i.stack.imgur.com/vvHEc.png

As shown in the diagram, an Observable serves as a continuous stream of events or data. In Angular, observables are commonly returned from methods like http.get and myinputBox.valueChanges.

Subscribing to an observable is what initiates the stream. Without subscribing (or using an async pipe), the values will not be emitted. It's similar to subscribing to receive newspapers or magazines - you won't start receiving them until you subscribe.

When you subscribe to an observable, you provide an observer. This observer includes three essential methods:

A method to handle each emission from the observable.
A method to manage any errors that occur.
A method for cleaning up tasks when the observer completes. This cleanup method is rarely needed when dealing with Angular's observables.

(I completely agree - navigating through documentation can feel like searching for the forest among trees. It's reassuring to know that efforts are being made to enhance the clarity of the docs.)

Answer 2

Let's take a look at this easy-to-understand visual illustration:

https://i.stack.imgur.com/vvHEc.png

As shown in the diagram, an Observable serves as a continuous stream of events or data. In Angular, observables are commonly returned from methods like http.get and myinputBox.valueChanges.

Subscribing to an observable is what initiates the stream. Without subscribing (or using an async pipe), the values will not be emitted. It's similar to subscribing to receive newspapers or magazines - you won't start receiving them until you subscribe.

When you subscribe to an observable, you provide an observer. This observer includes three essential methods:

A method to handle each emission from the observable.
A method to manage any errors that occur.
A method for cleaning up tasks when the observer completes. This cleanup method is rarely needed when dealing with Angular's observables.

(I completely agree - navigating through documentation can feel like searching for the forest among trees. It's reassuring to know that efforts are being made to enhance the clarity of the docs.)

Answer 3

Answer №2

Let's break it down with a simple analogy:-

Observable can be compared to a TV channel that broadcasts new shows. (( It provides the content(data) for you to watch, makes it a data source for you))
Your TV screen represents an Observer
Your TV screen (Observer) will only show you notifications about new shows or special events on a specific TV channel (Observable) if you are tuned in to that channel

(Observer tunes into Observable to receive new data/any event)

where observable serves as the content provider, tuning in is like a method/function, and Observer is typically on your end

Answer 4

Let's break it down with a simple analogy:-

Observable can be compared to a TV channel that broadcasts new shows. (( It provides the content(data) for you to watch, makes it a data source for you))
Your TV screen represents an Observer
Your TV screen (Observer) will only show you notifications about new shows or special events on a specific TV channel (Observable) if you are tuned in to that channel

(Observer tunes into Observable to receive new data/any event)

where observable serves as the content provider, tuning in is like a method/function, and Observer is typically on your end

Answer 5

Answer №3

An Observable can be likened to a variety of data sources, such as user inputs or HTTP requests.

In this example, we are creating our own custom observable.

    var observable = Observable.create((observer: any)=>{
       observer.next("Hello")
       observer.next("how are you")
       observer.complete()
    observer.next("This will not be sent to the observer")
});

The next() function is used to emit values to the observer
The complete() function indicates that the observable has completed

An Observer is someone who subscribes to the Observable.

observable.subscribe(
    (data: any) => console.log(data), // handle data
    (error: any) => console.log(error), // handle errors
    () => console.log('completed'); // handle completion

You can learn more about Observables here: http://reactivex.io/documentation/observable.html

Answer 6

An Observable can be likened to a variety of data sources, such as user inputs or HTTP requests.

In this example, we are creating our own custom observable.

    var observable = Observable.create((observer: any)=>{
       observer.next("Hello")
       observer.next("how are you")
       observer.complete()
    observer.next("This will not be sent to the observer")
});

The next() function is used to emit values to the observer
The complete() function indicates that the observable has completed

An Observer is someone who subscribes to the Observable.

observable.subscribe(
    (data: any) => console.log(data), // handle data
    (error: any) => console.log(error), // handle errors
    () => console.log('completed'); // handle completion

You can learn more about Observables here: http://reactivex.io/documentation/observable.html

Answer 7

Answer №4

Highlighted below are some key points:

1) Explanation: The "Observable and Observer" concept involves the passing of messages from a publisher to a subscriber.
2) Functionality flow:

An Observable is created
The Observer subscribes to the Observable
The Observable can send messages to the Observer
Each time a message is sent by the Observable, it is received by the Observer

3) Practical applications of Observable and Observer

When receiving responses from AJAX calls
During the execution of extensive tasks in a web browser

Answer 8

Highlighted below are some key points:

1) Explanation: The "Observable and Observer" concept involves the passing of messages from a publisher to a subscriber.
2) Functionality flow:

An Observable is created
The Observer subscribes to the Observable
The Observable can send messages to the Observer
Each time a message is sent by the Observable, it is received by the Observer

3) Practical applications of Observable and Observer

When receiving responses from AJAX calls
During the execution of extensive tasks in a web browser

Can you explain the concepts of observables, observers, and subscriptions in Angular?

Answer №1

Answer №2

Answer №3

Answer №4

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