Tips for creating an observable in Angular 2

Question

Tips for creating an observable in Angular 2

I'm having trouble declaring an observable and adding data to it in Angular 2. I've spent the last 5 hours trying to figure it out.
Here's what I've attempted:

this.products : Observable<array>;
var object = {"item": item};
this.products.subscribe(object)

Every approach I've tried results in an error.

I need to use an observable because I have an array of objects that changes frequently, but the ngFor in the template isn't updating the values. Can anyone offer some help?

http://pastebin.com/1cFXJHHk Here is my attempt at solving this issue

typescript angular

Answer 1

Answer №1

@pixelbits offered a comprehensive answer on utilizing raw observables effectively.

However, there seems to be a slight misunderstanding in your grasp of observables and reactive programming concepts. I recommend checking out this informative introduction to get started:

Uncover the basics of Reactive Programming - https://gist.github.com/staltz/868e7e9bc2a7b8c1f754

The use of the subscribe method in observables allows you to set up callbacks for notifications:

The first callback pertains to events
The second one relates to errors
The last one signifies completion

You can certainly apply event handling to append elements to a list, but it may not align with your specific requirements:

var someList = [];
let observable = (...)
observable.subscribe(data => {
  someList.push(data);
});

This technique proves valuable for tools or technologies based on events such as WebSockets, Firebase, etc. The referenced observable would be connected to them. For more insights on implementing this with Firebase, refer to this helpful answer:

I need a listener to see if my notifications table (node) has changed for real-time data checking

Answer 2

@pixelbits offered a comprehensive answer on utilizing raw observables effectively.

However, there seems to be a slight misunderstanding in your grasp of observables and reactive programming concepts. I recommend checking out this informative introduction to get started:

Uncover the basics of Reactive Programming - https://gist.github.com/staltz/868e7e9bc2a7b8c1f754

The use of the subscribe method in observables allows you to set up callbacks for notifications:

The first callback pertains to events
The second one relates to errors
The last one signifies completion

You can certainly apply event handling to append elements to a list, but it may not align with your specific requirements:

var someList = [];
let observable = (...)
observable.subscribe(data => {
  someList.push(data);
});

This technique proves valuable for tools or technologies based on events such as WebSockets, Firebase, etc. The referenced observable would be connected to them. For more insights on implementing this with Firebase, refer to this helpful answer:

I need a listener to see if my notifications table (node) has changed for real-time data checking

Answer 3

Answer №2

To initialize an Observable in a cold manner, you can utilize the create method as shown below:

myEvent:Rx.Observable<{item:Item}>;
myObserver: Rx.Observer<{item:Item}>;
constructor() {
    this.myEvent = Rx.Observable.create(o=>this.myObserver = o);
}
someEvent() {
    // Perform some action
    var $event = {item:new Item()};

    // Trigger the event object when something interesting occurs
    if(this.myObserver)
        this.myObserver.emit($event);
}

Answer 4

To initialize an Observable in a cold manner, you can utilize the create method as shown below:

myEvent:Rx.Observable<{item:Item}>;
myObserver: Rx.Observer<{item:Item}>;
constructor() {
    this.myEvent = Rx.Observable.create(o=>this.myObserver = o);
}
someEvent() {
    // Perform some action
    var $event = {item:new Item()};

    // Trigger the event object when something interesting occurs
    if(this.myObserver)
        this.myObserver.emit($event);
}

Tips for creating an observable in Angular 2

Answer №1

Answer №2

Similar questions

Upon clicking the button, the Angular Mat-Table with Reactive Forms fails to display any data, instead adding a blank row accompanied by errors

Troubleshooting Angular 4's ng-selected functionality

Managing HTTP requests with errors within a forEach loop in Angular 9

Interface-derived properties

TypeScript enables the use of optional arguments through method overloading

Unselected default option in Angular 4's select dropdown

How to eliminate file nesting in Visual Studio 2017

Exploring the integration of a standalone component in Angular 17 using an http service

"NODEJS: Exploring the Concept of Key-Value Pairs in Object

Guide to implementing ion-toggle for notifications with Ionic 2 and Angular 2

Utilizing combinedReducers will not prompt a re-render when dispatching actions

Oops! The last loader did not provide a Buffer or String as expected

Obtain values from a specific set, and then filter out values from an array that correspond to the index of that set into distinct arrays

Utilize the prototype feature from a versatile source

"Transferring a C# dictionary into a TypeScript Map: A step-by-step

What could be the reason for my npm package installed globally to not be able to utilize ts-node?

To trigger a Bootstrap 5 modal in a child component from a button click in the parent component in Angular without the need to install ng-bootstrap is possible with the following approach

What is the best RxJS operator to implement additional transformations following mapping?

Defining a type with limited knowledge: if you only have one key in the object

Don't forget to include the line 'import "reflect-metadata"' at the beginning of your entry point for Jest tests