Troubleshooting an Angular http.get issue involving the use of {responseType: 'text'}

Question

Troubleshooting an Angular http.get issue involving the use of {responseType: 'text'}

Each time I attempt to use {{requestType: 'text'}} within my http.get(url) call, an error occurs stating that only arrays and iterables are allowed for diffing. However, I am converting my object into an array. I need help understanding this issue and finding a solution.

When I exclude the RequestType, the array comes through without any problems and is displayed on my front end.

----service-----

 getAll(){
    const requestOptions: Object = {
      /* other options here */
      responseType: 'text'
    }
    return this.http.get<any>(this.url, requestOptions);
} 

---component .ts----- 

notificationsFass: any[];

  constructor(route: ActivatedRoute, private metaService: Meta, private notificationService: NotificationsFassService) {
    this.notificationsFass = [];
}


ngOnInit() {
    this.notificationService.getAll()
      .subscribe(notificationsFass => {
        this.notificationsFass = notificationsFass;
      }
        );
}

---html---

<div *ngFor="let m of notificationsFass">

---error----
ERROR Error: Error trying to diff '[{"incidentNumber":700,"createdByName":"FASS Notification","createdDate":"2019-03-27T09:18:15.000+0000"}]'. Only arrays and iterables are allowed

angular typescript http rxjs

Answer 1

Answer №1

After analyzing the json data in the error message, it is important to take the following actions:

To start off, create an interface with the name INotification. This interface will outline the available members within the deserialized json response.
Ensure that the method return types are strongly typed and provide the generic type argument in http.get<T>. When invoking http.get, it will automatically attempt to deserialize the json response from the server into an object graph. By specifying INotification[] as the return type, subsequent callers (like components) can safely utilize members of the returned type such as find or other Array.prototype functions, along with accessing defined members within instances stored in the array.

responseType: 'text' becomes essential only under circumstances where there is no response being emitted from the server or when the response contains text instead of json data. The former situation could occur during post, put, or delete requests, where the server may solely send a status without any message body included in the response.

Below is your service code modified based on the aforementioned suggestions.

notificationsFassService.ts

export interface INotification {
    incidentNumber: number;
    createdByName: string;
    createdDate: string;
}

export class NotificationsFassService {
    constructor (private readonly http: HttpClient) { }

    getAll():Observable<INotification[]> {
        return this.http.get<INotification[]>(this.url);
    } 
}

notificationsFassComponent.ts

export class NotificationsFassComponent implements OnInit {
    notificationsFass: INotification[];

    constructor(route: ActivatedRoute, private metaService: Meta, private notificationService: NotificationsFassService) {
        this.notificationsFass = [];
    }

    ngOnInit() {
        this.notificationService.getAll()
          .subscribe(notificationsFass => {
             this.notificationsFass = notificationsFass;
          });
    }
}

Answer 2

After analyzing the json data in the error message, it is important to take the following actions:

To start off, create an interface with the name INotification. This interface will outline the available members within the deserialized json response.
Ensure that the method return types are strongly typed and provide the generic type argument in http.get<T>. When invoking http.get, it will automatically attempt to deserialize the json response from the server into an object graph. By specifying INotification[] as the return type, subsequent callers (like components) can safely utilize members of the returned type such as find or other Array.prototype functions, along with accessing defined members within instances stored in the array.

responseType: 'text' becomes essential only under circumstances where there is no response being emitted from the server or when the response contains text instead of json data. The former situation could occur during post, put, or delete requests, where the server may solely send a status without any message body included in the response.

Below is your service code modified based on the aforementioned suggestions.

notificationsFassService.ts

export interface INotification {
    incidentNumber: number;
    createdByName: string;
    createdDate: string;
}

export class NotificationsFassService {
    constructor (private readonly http: HttpClient) { }

    getAll():Observable<INotification[]> {
        return this.http.get<INotification[]>(this.url);
    } 
}

notificationsFassComponent.ts

export class NotificationsFassComponent implements OnInit {
    notificationsFass: INotification[];

    constructor(route: ActivatedRoute, private metaService: Meta, private notificationService: NotificationsFassService) {
        this.notificationsFass = [];
    }

    ngOnInit() {
        this.notificationService.getAll()
          .subscribe(notificationsFass => {
             this.notificationsFass = notificationsFass;
          });
    }
}

Troubleshooting an Angular http.get issue involving the use of {responseType: 'text'}

Answer №1

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