Guide to executing CRUD actions on a list observable with the help of the async pipe in Angular

Question

Guide to executing CRUD actions on a list observable with the help of the async pipe in Angular

Up until now, I've been used to looping through lists in my Angular apps using the ngFor directive without utilizing the async pipe. However, today I came across the async pipe and decided to give it a try.

So here's an example of a component template where I implemented it:

<ng-container *ngIf="todos$ | async as todos">
  <div *ngFor="let todo of todos">{{ todo.content }}</div>
</ng-container>

And in the sample component class:

this.todos$ = this.todoService.getAllTodos();

My current dilemma is figuring out how to perform add, edit, or delete operations on the todos$ observable.

angular typescript rxjs

Answer 1

Answer №1

To start, it's important to note that requests made by the httpClient are self-completing, meaning they cannot emit any new values after completion.

A solution to this is to utilize a separate Observable or Subject. A suitable option in this scenario would be the BehaviourSubject.

First, you establish:

this.todos$ = new BehaviourSubject(null);

It should be highlighted that the default value of todos$ is set to null. To avoid using *ngIf, you can provide an empty array as an alternative.

After the request has finished, you can emit the response:

this.todoService.getAllTodos()
  .subscribe(response => {
    this.todos$.next(response);
  });

If there comes a time when you need to modify the data, you can retrieve the current value (from the BehaviourSubject), make changes to it, and then re-emit it. For instance, adding a new item could be done like this:

this.todos$.next([newItem, ...this.todos$.value]);

Answer 2

To start, it's important to note that requests made by the httpClient are self-completing, meaning they cannot emit any new values after completion.

A solution to this is to utilize a separate Observable or Subject. A suitable option in this scenario would be the BehaviourSubject.

First, you establish:

this.todos$ = new BehaviourSubject(null);

It should be highlighted that the default value of todos$ is set to null. To avoid using *ngIf, you can provide an empty array as an alternative.

After the request has finished, you can emit the response:

this.todoService.getAllTodos()
  .subscribe(response => {
    this.todos$.next(response);
  });

If there comes a time when you need to modify the data, you can retrieve the current value (from the BehaviourSubject), make changes to it, and then re-emit it. For instance, adding a new item could be done like this:

this.todos$.next([newItem, ...this.todos$.value]);

Guide to executing CRUD actions on a list observable with the help of the async pipe in Angular

Answer №1

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