How to solve catch error in Observable in angular 8?

Question

I do error handler code, but I got error in catch. undefined method.

This is my serivce.ts code.

import { Injectable } from "@angular/core";
import { HttpClient, HttpErrorResponse } from "@angular/common/http";
import { user } from "./user";
import { Observable } from "rxjs";
import "rxjs/add/operator/catch";
import "rxjs/add/Observable/throw";
@Injectable({
  providedIn: "root"
})
export class DemoService {
  private url: string = "/assets/demo/user.json";
  constructor(private http: HttpClient) {}

  getuserdetails(): Observable<user[]> {
    return this.http.get<user[]>(this.url).catch(this.errorHandler);
  }
  errorHandler(error: HttpErrorResponse) {
    return Observable.throw(error.message || "server error.");
  }
}

This is my app.component.ts file code

 public userdetails = [];
  public errorMsg;
  constructor(private user: DemoService) {}
  ngOnInit() {
    this.user
      .getuserdetails()
      .subscribe(
        $data => (this.userdetails = $data),
        error => (this.errorMsg = error)
      );
  } 

I got error in catch. and error message is Property 'catch' does not exist on type 'Observable'.

Answer 1

You can use catchError in rxjs/operators for this. Try it as follows.

import { catchError } from 'rxjs/operators';

export class DemoService {

    getuserdetails(): Observable<user[]> {
        return this.http.get<user[]>(this.url)
            .pipe(catchError(this.errorHandler))
    }
    errorHandler(error: HttpErrorResponse) {
        return Observable.throw(error.message || "server error.");
    }
}

Answer 2

In the last version of rxjs you should use:

return return this.http.get<user[]>(this.url)
                  .subscribe((r:Author) => console.log("GOOD"),
                                    err => console.log("ERROR))

Answer 3

Best way to catch error on observable is:

this.http.get<user[]>(this.url).pipe(
   tap(),
   catchError(err => { return this.errorHandler(err) }
)

If this.http.get() is an Promise lave it like You did in Your code .catch(...) is ok. Try to have catchError(...) at the end of pipe or before finalize(..) if You use it.

Before Observables had no .pipe() and You where chaining operations like in Promises so they change name .then() to i think flatMap() and .catch() to catchError() So programmer know are it is Observable or Promise.