Angular Error - TS2322: The specified type of 'Object | null' cannot be assigned to 'NgIterable<any> | null | undefined'

I encountered an error in

homes.component.html

while trying to run my Angular project to showcase a list of homes from a JSON file.

https://i.stack.imgur.com/D0vLQ.jpg

Json File

 [
    {
      "image_url": "https://images.unsplash.com/photo-1460317442991-0ec209397118?auto=format&fit=crop&w=500&q=80",
      "type": "Apartment",
      "location": "New York",
      "title": "Superb duplex apartment in the historical centre"
    },
    ...
    {
      "image_url": "https://images.unsplash.com/photo-1460317442991-0ec209397118?auto=format&fit=crop&w=500&q=80",
      "type": "Apartment",
      "location": "New York",
      "title": "Rustic Apartment in Downtown"
    }
 ]

homes.component.html

<div class="uk-container uk-padding">
    <h1>Homes</h1>
    <div *ngFor="let home of homes$ | async">
        <div class="uk-card">
            ...
</div>

data.service.ts

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Injectable({
  providedIn: 'root'
})
export class DataService {

  constructor(private httpClient: HttpClient) { }

  getHomes() {
    return this.httpClient.get('assets/homes.json');
  }
}

homes.component.ts

import { Component, OnInit } from '@angular/core';
import { DataService } from '../data.service';

@Component({
  selector: 'app-homes',
  templateUrl: './homes.component.html'
})
export class HomesComponent implements OnInit {

  homes$ = this.dataService.getHomes();

  constructor(private dataService: DataService) { }

  ngOnInit() {
  }

}

The intention is to present a collection of homes from a JSON file complete with images and corresponding descriptions.

Answer №1

Ensure that in your resources/home.json file, the information is structured as an array.

[
    {
        "image_url": "",
        "type": "",
        "location": "",
        "title": ""
    }
]

Answer №2

Verify if the result generated by the retrieveResidence function is an array. It could be advantageous to move the declaration of properties$ into the ngOnInit phase.

Answer №3

After examining your code, I have replicated your setup to address the issue at hand. Here are the steps I took to resolve the problem:

  1. Ensure that both HttpClientModule and DataServices are correctly imported and defined in your project.
  2. homes$ must be initialized within the ngOnInit() { ... } lifecycle to ensure proper functionality with the async pipe.
  3. I created a TypeScript definition file named json.d.ts to facilitate importing JSON files without direct HTTP requests, enabling parsing as an object. Additionally, I included the necessary configurations in the tsconfig.json TypeScript file:
"compilerOptions": {
  ...
  "resolveJsonModule": true,
  "esModuleInterop": true
  ...
}
  1. Subsequently, the DataService file should resemble the following structure :
...
...
import data from './home.json';
import { of } from 'rxjs';
...
...
export class DataService {

  getHomes() {
    return of(data);
  }
...
...
}

  1. Lastly, I incorporated a basic check using *ngIf in the HTML view:
 <ng-container *ngIf="homes$">
    <div *ngFor="let home of homes$ | async">
    </div>
 </ng-container>

If you would like to explore the complete solution on StackBlitz, please visit here. Feel free to reach out if you notice any errors or suggestions for improvement.

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