Steps for converting an observable http request into a promise request

Question

Steps for converting an observable http request into a promise request

Here is a link to my service file: https://i.sstatic.net/8dsMx.png This is the TypeScript file for my components: https://i.sstatic.net/of6sx.png And these are the response models: https://i.sstatic.net/U8RUQ.png https://i.sstatic.net/7baTj.png

I am currently facing difficulties with displaying asynchronously fetched data in my component's TypeScript file using an Observable-based service. I have learned that converting the service to Promise-based structure could help, but I am struggling with implementing the responseModel provided by Observables in a Promise-based setup. Any guidance on this issue would be greatly appreciated.

Also, here are some outputs from my project: https://i.sstatic.net/rIRjt.png

angular typescript async-await promise angular-promise

Answer 1

Answer №1

If you're working with RxJS version 7.8.0, my suggestion would be to utilize the lastValueFrom method

For example:

import { HttpClient } from '@angular/common/http';
import { lastValueFrom, take } from 'rxjs';

class YourService {

  constructor(
    private readonly httpClient: HttpClient,
  ) {}

  async yourFunction(): Promise<YourTypeOrInterface> {
    const request$ = this.httpClient.get(yourUrl).pipe(take(1));

    return await lastValueFrom<YourTypeOrInterface>(request$);
  }

}

.toPromise() is no longer recommended and will be phased out completely in RxJS 8.

Answer 2

If you're working with RxJS version 7.8.0, my suggestion would be to utilize the lastValueFrom method

For example:

import { HttpClient } from '@angular/common/http';
import { lastValueFrom, take } from 'rxjs';

class YourService {

  constructor(
    private readonly httpClient: HttpClient,
  ) {}

  async yourFunction(): Promise<YourTypeOrInterface> {
    const request$ = this.httpClient.get(yourUrl).pipe(take(1));

    return await lastValueFrom<YourTypeOrInterface>(request$);
  }

}

.toPromise() is no longer recommended and will be phased out completely in RxJS 8.

Answer 3

Answer №2

Observables come equipped with a method called .toPromise()

const response = await this.currencyService.getAllByDate(...).toPromise()

MODIFY Ensure that your call stack remains asynchronous throughout

async ngOnInit(): Promise<void> {
    await this.getAllByDate();
    ...
}

async getAllByDate() {
    let date;
    if (this.selectedDate == null) {
        date = new Date(Date.now()).setHours(3,0,0,0);
    } else {
        date = new Date(this.selectedDate).setHours(3,0,0,0);
    }

    const response = await this.currencyService.getAllByDate(new Date(date)).toPromise();

    if (response && isArray(response.data)) {
        this.currencies = response.data;
        this.currencies.push(newCurrency);
    }
}

REVISE As the usage of toPromise() is being phased out, in future versions you would need to create your own promises

const promise = new Promise((resolve, reject) => {
    this.currencyService.getAllByDate(...)
        .pipe(take(1))
        .subscribe({ complete: resolve, error: reject })
});

const response = await promise;

Answer 4

Observables come equipped with a method called .toPromise()

const response = await this.currencyService.getAllByDate(...).toPromise()

MODIFY Ensure that your call stack remains asynchronous throughout

async ngOnInit(): Promise<void> {
    await this.getAllByDate();
    ...
}

async getAllByDate() {
    let date;
    if (this.selectedDate == null) {
        date = new Date(Date.now()).setHours(3,0,0,0);
    } else {
        date = new Date(this.selectedDate).setHours(3,0,0,0);
    }

    const response = await this.currencyService.getAllByDate(new Date(date)).toPromise();

    if (response && isArray(response.data)) {
        this.currencies = response.data;
        this.currencies.push(newCurrency);
    }
}

REVISE As the usage of toPromise() is being phased out, in future versions you would need to create your own promises

const promise = new Promise((resolve, reject) => {
    this.currencyService.getAllByDate(...)
        .pipe(take(1))
        .subscribe({ complete: resolve, error: reject })
});

const response = await promise;

Steps for converting an observable http request into a promise request

Answer №1

Answer №2

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