Angular - Issue with Function Observable<number> in Development

Question

Angular - Issue with Function Observable<number> in Development

Currently, I'm working on writing TypeScript code for a component. Within this TypeScript class, I have created a function that is meant to return a number representing the length of an array. My goal is to have this function work like an Observable. However, I encountered an error stating "number is not assignable to type Observable."

  NumItemsCart():Observable<number>{
    let string_items = '';
    let array_temp = [];
    let num_items=0;
    
    string_items = localStorage.getItem('ecmm_list_shopcart');

    array_temp= cadena_items.split(',')
    
    num_items= array_temp.length -1

    return num_items
  }

angular typescript observable

Answer 1

Answer №1

The reason for this issue is due to the discrepancy between the expected return type (Observable<number>) and the actual return type (number). One easy solution to return a value as an observable is by utilizing the of() function from RxJS (refer to documentation here)

By simplifying your code slightly, the revised version should resemble something like this:

import { of } from 'rxjs';

getCartItemCount(): Observable<number> {
    let itemsString = '';
    let tempArray = [];

    itemsString = localStorage.getItem('cart_items');

    tempArray = itemsString.split(',')

    return of(tempArray.length - 1)
}


const itemCount: Observable<number> = getCartItemCount()

Answer 2

The reason for this issue is due to the discrepancy between the expected return type (Observable<number>) and the actual return type (number). One easy solution to return a value as an observable is by utilizing the of() function from RxJS (refer to documentation here)

By simplifying your code slightly, the revised version should resemble something like this:

import { of } from 'rxjs';

getCartItemCount(): Observable<number> {
    let itemsString = '';
    let tempArray = [];

    itemsString = localStorage.getItem('cart_items');

    tempArray = itemsString.split(',')

    return of(tempArray.length - 1)
}


const itemCount: Observable<number> = getCartItemCount()

Answer 3

Answer №2

The problem at hand is quite simple: The NumItemsCart method is meant to return an Observable of a number, but instead it is returning just a plain number.

All that needs to be done is to transform num_items into an Observable by utilizing the rxjs of operator.

return of(num_items);

Answer 4

The problem at hand is quite simple: The NumItemsCart method is meant to return an Observable of a number, but instead it is returning just a plain number.

All that needs to be done is to transform num_items into an Observable by utilizing the rxjs of operator.

return of(num_items);

Angular - Issue with Function Observable<number> in Development

Answer №1

Answer №2

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