Angular2 # TypeScript Observable error - http

Question

I have an input field and when the user types a search string I want to wait for the user to stop typing for at least 300 milliseconds (debounce) before doing a _heroService http request. Only changed search values make it through to the service (distinctUntilChanged). The switchMap returns a new observable that combines these _heroService observables, re-arranges them in their original request order, and delivers to subscribers only the most recent search results.
I am using Angular 2.0.0-beta.0 and TypeScript 1.7.5.
How do I get this thing working correct?
I get compile error:
Error:(33, 20) TS2345: Argument of type '(value: string) => Subscription<Hero[]>' is not assignable to parameter of type '(x: {}, ix: number) => Observable<any>'.Type 'Subscription<Hero[]>' is not assignable to type 'Observable<any>'. Property 'source' is missing in type 'Subscription<Hero[]>'.
Error:(36, 31) TS2322: Type 'Hero[]' is not assignable to type 'Observable<Hero[]>'. Property 'source' is missing in type 'Hero[]'.
Run time error (after typing first key in search input field):
EXCEPTION: TypeError: unknown type returned
STACKTRACE:
TypeError: unknown type returned
at Object.subscribeToResult (http://localhost:3000/rxjs/bundles/Rx.js:7082:25)
at SwitchMapSubscriber._next (http://localhost:3000/rxjs/bundles/Rx.js:5523:63)
at SwitchMapSubscriber.Subscriber.next (http://localhost:3000/rxjs/bundles/Rx.js:9500:14)
...
-----async gap----- Error at _getStacktraceWithUncaughtError
EXCEPTION: Invalid argument '[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]' for pipe 'AsyncPipe' in [heroes | async in Test#4:16]
test1.ts
import {bootstrap} from 'angular2/platform/browser';
import {Component} from 'angular2/core';
import {HTTP_PROVIDERS} from 'angular2/http';
import {Observable} from 'rxjs/Observable';
import {Subject} from 'rxjs/Subject';
import 'rxjs/Rx';
import {Hero} from './hero';
import {HeroService} from './hero.service';
#Component({
selector: 'my-app',
template: `
<h3>Test</h3>
Search <input #inputUser (keyup)="search(inputUser.value)"/><br>
<ul>
<li *ngFor="#hero of heroes | async">{{hero.name}}</li>
</ul>
`,
providers: [HeroService, HTTP_PROVIDERS]
})
export class Test {
public errorMessage: string;
private _searchTermStream = new Subject<string>();
private heroes: Observable<Hero[]> = this._searchTermStream
.debounceTime(300)
.distinctUntilChanged()
.switchMap((value: string) =>
this._heroService.searchHeroes(value)
.subscribe(
heroes => this.heroes = heroes,
error => this.errorMessage = <any>error)
)
constructor (private _heroService: HeroService) {}
search(value: string) {
this._searchTermStream.next(value);
}
}
bootstrap(Test);
hero.ts
export interface Hero {
_id: number,
name: string
}
hero.service.ts
import {Injectable} from 'angular2/core';
import {Http, Response} from 'angular2/http';
import {Headers, RequestOptions} from 'angular2/http';
import {Observable} from 'rxjs/Observable';
import 'rxjs/Rx';
import {Hero} from './hero';
#Injectable()
export class HeroService {
private _heroesUrl = 'api/heroes';
constructor (private http: Http) {}
getHeroes () {
return this.http.get(this._heroesUrl)
.map(res => <Hero[]> res.json())
.do(data => console.log(data))
.catch(this.handleError);
}
searchHeroes (value) {
return this.http.get(this._heroesUrl + '/search/' + value )
.map(res => <Hero[]> res.json())
.do(data => console.log(data))
.catch(this.handleError);
}
addHero (name: string) : Observable<Hero> {
let body = JSON.stringify({name});
let headers = new Headers({ 'Content-Type': 'application/json' });
let options = new RequestOptions({ headers: headers });
return this.http.post(this._heroesUrl, body, options)
.map(res => <Hero> res.json())
.do(data => console.log(data))
.catch(this.handleError)
}
private handleError (error: Response) {
// in a real world app, we may send the server to some remote logging infrastructure
// instead of just logging it to the console
console.log(error);
return Observable.throw('Internal server error');
}
}
index.html
<!DOCTYPE html>
<html>
<head>
<base href="/">
<script src="angular2/bundles/angular2-polyfills.js"></script>
<script src="typescript/lib/typescript.js"></script>
<script src="systemjs/dist/system.js"></script>
<script src="angular2/bundles/router.dev.js"></script>
<script src="rxjs/bundles/Rx.js"></script>
<script src="angular2/bundles/angular2.js"></script>
<script src="angular2/bundles/http.dev.js"></script>
<link rel="stylesheet" href="node_modules/bootstrap/dist/css/bootstrap.min.css">
<script>
System.config({
transpiler: 'typescript',
typescriptOptions: { emitDecoratorMetadata: true },
packages: {'components': {defaultExtension: 'ts'}}
});
System.import('components/test1')
.then(null, console.error.bind(console));
</script>
</head>
<body>
<my-app>Loading...</my-app>
</body>
</html>
Here is another version 'test2.ts' that works fine doing a http request after every (keyup) event:
import {bootstrap} from 'angular2/platform/browser';
import {Component} from 'angular2/core';
import {HTTP_PROVIDERS} from 'angular2/http';
import {Hero} from './hero';
import {HeroService} from './hero.service';
#Component({
selector: 'my-app',
template: `
<h3>Test</h3>
Search <input #inputUser (keyup)="search(inputUser.value)"/><br>
<ul>
<li *ngFor="#hero of heroes">{{hero.name}}</li>
</ul>
`,
providers: [HeroService, HTTP_PROVIDERS]
})
export class Test {
public heroes:Hero[] = [];
public errorMessage: string;
constructor (private _heroService: HeroService) {}
search(value: string) {
if (value) {
this._heroService.searchHeroes(value)
.subscribe(
heroes => this.heroes = heroes,
error => this.errorMessage = <any>error);
}
else {
this.heroes = [];
}
}
}
bootstrap(Test);

Answer 1

.subscribe(...) returns a Subscription, not an Observable.
Remove the subscribe(...) or replace it by a .map(...) and use .subscribe(...) when you access it to get the values.