Error NG0900 An error occurred while trying to compare. Only arrays and iterable objects allowed
P粉226667290
P粉226667290 2024-02-25 19:15:04
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Using *ngFor I am able to render the data but it throws this error

Error Error: NG0900: An error occurred while trying to compare '[object Object]'. Only arrays and iterable objects allowed

This is my service method

async getEditions(): Promise<Observable<Cigales>> {
    return this.http.get<Cigales>(url+"/candidates/editions", httpOptions).pipe(
      tap((getEditions: Cigales) => this.log('getEditions' + getEditions)),
      catchError(this.handleError<Cigales>('getEditions'))
    );
  }

This is my component method

editions: Cigale[] = [];

  async getEditions(): Promise<void> {
    await this.CigalesService.getEditions().then(res=> {
      res.subscribe(data => {
        this.editions = [];
        this.editions = data.content;
      })
    })
  }

This is my Cigales interface

export interface Cigales {
  content: Array<Cigale>,
  pageable: pageable,
  last: string;
  totalPages: string;
  totalElements: string;
  size: string;
  number: string;
  sort: sort;
  first: string;
  numberOfElements: string;
  empty: string;
}

export interface Cigale {
  id?: string;
  eventName: string;
  eventStartDate: string;
  eventEndDate: string;
}

type sort = {
  empty: boolean,
  sorted: boolean,
  unsorted: boolean
}

type pageable = {
  sort: sort,
  offset: string;
  pageNumber: string;
  pageSize: string;
  paged: string;
  unpaged: string;
}

This is my component.html

<tr *ngFor="let item of editions">
        <td>{{item.eventName}}</td>
        <td>{{item.eventStartDate}}</td>
        <td>{{item.eventEndDate}}</td>
        <td>
          <a class="d-inline" role="button" data-bs-toggle="modal" data-bs-target="#application-modal"><i class="bi bi-clipboard"></i></a>
          <a class="d-inline" role="button" data-bs-toggle="modal" data-bs-target="#application-modal"><i class="bi bi-pencil-square"></i></a>
        </td>
      </tr>

Console.log(this.editions) and I get an array of two objects

Console results

EDIT: I tried Array.isArray(this.editions) and it returns true

P粉226667290
P粉226667290

reply all(1)
P粉852578075

First of all, the error you are facing is related to you trying to use an object instead of an array as the data source for the *ngFor directive.

Secondly, try assigning data to this.editions, for example:

async getEditions(): Promise {
  await this.CigalesService.getEditions().then(res=> {
    res.subscribe(data => {
      this.editions= [...data.content];
    })
  })
}

Additionally, I recommend that you avoid using Promises in Angular applications and instead make your code more reactive by leveraging subscriptions.

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