Error encountered in Angular 2 with RXJS Observable: Unable to call function catch() on this.http.get(...).map(...) due to TypeError

Everything was running smoothly with my Service until today, when I encountered the following error:

TypeError: this.http.get(...).map(...).catch is not a function. 

Upon debugging the code, it crashes at the catch method.

import { Test } from "./home.component";
import { Injectable }     from "@angular/core";
import { Inject } from "@angular/core";
import { Http , Response  } from "@angular/http";
import { Observable }     from "rxjs/Observable";

@Injectable()
export class HomeService {
   public constructor(@Inject(Http)  private http: Http) {}

   public getData (): Observable<Test []> {
        return this.http.get("./src/app/home/home-data.json")
            .map(this.extractData).catch(this.handleError);
    }

    public extractData(res: Response) {
        let body = res.json();
        return body.data || { };
    }

    public handleError (error: any) {
        // In a real world app, we might use a remote logging infrastructure
        // We'd also dig deeper into the error to get a better message
        let errMsg = (error.message) ? error.message :
            error.status ? `${error.status} - ${error.statusText}` : "Server error";
        console.error(errMsg); // log to console instead
        return Observable.throw(errMsg);
    }
  }

Answer №1

It appears that the catch operator has not been imported.

One possible solution is to import it using the following code:

import 'rxjs/add/operator/catch'

Alternatively, you can import more methods for observables by using the following code:

import 'rxjs/Rx';

For further information, refer to this question:

  • Angular 2 HTTP GET with TypeScript error http.get(...).map is not a function in [null]

Answer №2

Encountering a similar challenge, I discovered that the issue stemmed from importing the necessary modules multiple times within Module.ts.

Answer №3

Remember to capitalize the 'O' in 'rxjs/Observable'. Using a lowercase 'o' can cause errors that are quite mysterious!

Make sure to import it correctly like so:

import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/throw';

It may take some time to figure out, as most imports use lowercase names. This was a new discovery for me and hopefully will be helpful to others :)

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