Angular2: TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined

Question

I'm new to observables and experimenting with an basic autocomplete variation of Christoph Burgdorf's Observables in Angular2 blog. Running this code produces:

EXCEPTION: TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined

after issuing the REST get call in ingredientservice...rawsearch. The alert also pops with an [object Object] message. I've verified the endpoint is running fine.

Any recommendations on how to debug this would be greatly appreciated.

ingredientservice.ts waits for a change on a text string, debounces it and performs a REST call to get autocomplete matches from an endpoint.

import {Injectable} from 'angular2/core';
import {Http} from 'angular2/http';
import {Observable} from 'rxjs/Observable';
import 'rxjs/add/operator/debounceTime';
import 'rxjs/add/operator/distinctUntilChanged';
import 'rxjs/add/operator/switchMap';
import 'rxjs/add/operator/map';

@Injectable()
export class IngredientService {
  endpoint_url: String = "http://localhost:5000/ingredient/";
  results: Observable<Array<string>>;
  constructor(private http: Http) { }

  search(terms: Observable<string>, debounceDuration = 400) {
    return terms.debounceTime(debounceDuration)
      .distinctUntilChanged()
      .switchMap(term => this.rawSearch(term));
  }

  getData: Object[];
  rawSearch(term: string) {
    console.log(term);

    this.http.get(this.endpoint_url + term)
      .subscribe(
      res => {
        this.getData = res.json();
        console.log(this.getData);
        return this.getData;
      },
      error => alert(error));
  }
}

for completeness I have included the component ingredientsearch.ts

import {Component} from 'angular2/core';
import {Control} from 'angular2/common';
import {IngredientService} from './ingredientservice';
import {Observable} from 'rxjs/Observable';

@Component({
  selector: 'ingredient-search',
  template: `
    <div>
      <h2>Ingredient Search</h2>
      <input type="text" [ngFormControl]="term"/>
      <ul>
        <li *ngFor="#item of items | async">{{item}}</li>
      </ul>
    </div>
  `,
  providers: [IngredientService]
})

export class IngredientSearch {
  items: Observable<Array<string>>;
  term = new Control();
  constructor(private ingredientService: IngredientService) {
    console.log("About to call service");
    this.items = ingredientService.search(this.term.valueChanges);
  }
}

Updated code snippet with recommended fix.

rawSearch(term: string) {
    this.getData = ([]);
    this.http.get(this.endpoint_url + term)
      .subscribe(
      res => {
        this.getData = res.json();
        console.log(this.getData);
        return this.getData;
      },
      error => {
        alert(error);
      });
    return this.getData;
  }

Answer 1

Items is undefined when the view is bound - before the service returns. Initialize items to an empty array. Or use an Observable wrapper and the async operator in your template.