我收到错误TypeError：undefined是不可迭代的（无法读取属性Symbol（Symbol.iterator））错误

Question

I am using angular 8 at front end and java spring boot at back end while running the application I am getting this error. I am new to angular and I guess the error is because of response body from back end but I couldn't solve it.

I have tried the other answers but nothing seems to work.

auth.service.ts

// Method from server should return QueryResultsModel(items: any[], totalsCount: number)
    // items => filtered/sorted result
    findUsers(queryParams: QueryParamsModel): Observable<QueryResultsModel> {
        const httpHeaders = new HttpHeaders();
        httpHeaders.set('Content-Type', 'application/json');
        return this.http.post<QueryResultsModel>(API_USERS_URL + '/use' + '/findUsers', queryParams, { headers: httpHeaders});
    }

Web service java spring boot

// Get All User
@PostMapping(value = "/user/use/findUsers")
public ResponseEntity<List<User>> getAllUserFind() {
    try {
        return new ResponseEntity<>((List<User>)userService.getAllUser(), HttpStatus.OK);
    } catch (Exception e) {
        return new ResponseEntity<>(null, HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

Answer 1

You need to find out the exact cause of error by gracefully catching the error in your observable resolution. Use

return this.http.post<QueryResultsModel>(API_USERS_URL + '/use' + '/findUsers', queryParams, { headers: httpHeaders})
.pipe(catchError(error)=>{
    console.log(error);
    return of(null);
});

This will print out the exact error on your console. Remember to import Rx Operators.

import { of } from 'rxjs';
import { catchError } from 'rxjs/operators';

Answer 2

Metronic theme ?

It's an amazing Template.

QueryResultsModel is a Model

// fields
items: any[]; <---- This is where you should iterate 
importedCount?: number;
activeCount?: number;
totalCount: number;
errorMessage: string;

Good Luck !