Issue
In TypeScript / Angular, you would usually call a function that returns an observable and subscribe to it in a component like this:
this.productsService.getProduct().subscribe((product) => { this.product = product });
This is fine when the code runs in a class that manages data, but in my opinion this should not be handled in the component. I may be wrong but i think the job of a component should be to ask for and display data without handling how the it is retrieved.
In the angular template you can do this to subscribe to and display the result of an observable:
<h1>{{ product.title | async }}</h1>
Is it possible to have something like this in the component class? My component displays a form and checks if a date is valid after input. Submitting the form is blocked until the value is valid and i want to keep all the logic behind it in the service which should subscribe to the AJAX call, the component only checks if it got a valid date.
class FormComponent {
datechangeCallback(date) {
this.dateIsValid$ = this.dateService.checkDate(date);
}
submit() {
if (this.dateIsValid$ === true) {
// handle form submission...
}
}
}
Solution
You can convert rxjs Observables to ES6 Promises and then use the async-await
syntax to get the data without observable subscription.
Service:
export class DateService {
constructor(private http: HttpClient) {}
async isDateValid(date): Promise<boolean> {
let data = await this.http.post(url, date, httpOptions).toPromise();
let isValid: boolean;
// perform your validation and logic below and store the result in isValid variable
return isValid;
}
}
Component:
class FormComponent {
async datechangeCallback(date) {
this.dateIsValid = await this.dateService.isDateValid(date);
}
submit() {
if (this.dateIsValid) {
// handle form submission...
}
}
}
P.S:
If this is a simple HTTP request, which completes on receiving one value, then using Promises won't hurt. But if this obersvable produces some continuous stream of values, then using Promises isn't the best solution and you have to revert back to rxjs observables.
Answered By - Shravan
0 comments:
Post a Comment
Note: Only a member of this blog may post a comment.