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hero.service.ts
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hero.service.ts
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import { Injectable, Inject, Optional } from '@angular/core';
import { APP_BASE_HREF } from '@angular/common';
import { HttpClient, HttpHeaders }from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import { of } from 'rxjs/observable/of';
import { catchError, map, tap } from 'rxjs/operators';
import { Hero } from './hero';
import { MessageService } from './message.service';
const httpOptions = {
headers: new HttpHeaders({ 'Content-Type': 'application/json' })
};
@Injectable()
export class HeroService {
private heroesUrl = 'api/heroes'; // URL to web api
// #docregion ctor
constructor(
private http: HttpClient,
private messageService: MessageService,
@Optional() @Inject(APP_BASE_HREF) origin: string) {
this.heroesUrl = `${origin}${this.heroesUrl}`;
}
// #enddocregion ctor
/** GET heroes from the server */
getHeroes (): Observable<Hero[]> {
return this.http.get<Hero[]>(this.heroesUrl)
.pipe(
tap(heroes => this.log(`fetched heroes`)),
catchError(this.handleError('getHeroes', []))
);
}
/** GET hero by id. Return `undefined` when id not found */
getHeroNo404<Data>(id: number): Observable<Hero> {
const url = `${this.heroesUrl}/?id=${id}`;
return this.http.get<Hero[]>(url)
.pipe(
map(heroes => heroes[0]), // returns a {0|1} element array
tap(h => {
const outcome = h ? `fetched` : `did not find`;
this.log(`${outcome} hero id=${id}`);
}),
catchError(this.handleError<Hero>(`getHero id=${id}`))
);
}
/** GET hero by id. Will 404 if id not found */
getHero(id: number): Observable<Hero> {
const url = `${this.heroesUrl}/${id}`;
return this.http.get<Hero>(url).pipe(
tap(_ => this.log(`fetched hero id=${id}`)),
catchError(this.handleError<Hero>(`getHero id=${id}`))
);
}
/* GET heroes whose name contains search term */
searchHeroes(term: string): Observable<Hero[]> {
if (!term.trim()) {
// if not search term, return empty hero array.
return of([]);
}
return this.http.get<Hero[]>(`api/heroes/?name=${term}`).pipe(
tap(_ => this.log(`found heroes matching "${term}"`)),
catchError(this.handleError<Hero[]>('searchHeroes', []))
);
}
//////// Save methods //////////
/** POST: add a new hero to the server */
addHero (name: string): Observable<Hero> {
const hero = { name };
return this.http.post<Hero>(this.heroesUrl, hero, httpOptions).pipe(
tap((hero: Hero) => this.log(`added hero w/ id=${hero.id}`)),
catchError(this.handleError<Hero>('addHero'))
);
}
/** DELETE: delete the hero from the server */
deleteHero (hero: Hero | number): Observable<Hero> {
const id = typeof hero === 'number' ? hero : hero.id;
const url = `${this.heroesUrl}/${id}`;
return this.http.delete<Hero>(url, httpOptions).pipe(
tap(_ => this.log(`deleted hero id=${id}`)),
catchError(this.handleError<Hero>('deleteHero'))
);
}
/** PUT: update the hero on the server */
updateHero (hero: Hero): Observable<any> {
return this.http.put(this.heroesUrl, hero, httpOptions).pipe(
tap(_ => this.log(`updated hero id=${hero.id}`)),
catchError(this.handleError<any>('updateHero'))
);
}
/**
* Handle Http operation that failed.
* Let the app continue.
* @param operation - name of the operation that failed
* @param result - optional value to return as the observable result
*/
private handleError<T> (operation = 'operation', result?: T) {
return (error: any): Observable<T> => {
// TODO: send the error to remote logging infrastructure
console.error(error); // log to console instead
// TODO: better job of transforming error for user consumption
this.log(`${operation} failed: ${error.message}`);
// Let the app keep running by returning an empty result.
return of(result as T);
};
}
/** Log a HeroService message with the MessageService */
private log(message: string) {
this.messageService.add('HeroService: ' + message);
}
}