[英]Rxjs Nested observer is not executed
我已經閱讀了很多關於如何在 RxJs 和 Angular 中嵌套觀察者的文檔、文章和不同的線程,但我仍然遺漏了一些東西並且最終無法得到結果。
頁面.ts
export class LiabilitiesPage implements OnInit {
constructor(
private liabilityService: LiabilityService,
private router: Router
) {}
refreshLiabilities() {
// Get the liabilities
console.log('refreshing') // passing there
this.liabilityService.getAllLiabilities().subscribe(
(response: Liability[]) => {
console.log(response); // <=== Never pass there !
if (response) {
this.liabilities = response;
} else {
// empty response code
}
}, error => {
// response error code (never passing there either)
}
}
}
liability.service.ts
// all the needed imports
@Injectable({
providedIn: 'root'
})
export class LiabilityService {
constructor(
private authService: AuthService,
private http: HttpClient,
) {}
// first try : Do not send the http request
getAllLiabilities(): Observable<Liability[]> {
return this.authService.getOptions()
.pipe(
tap(options => this.http.get<Liability[]>(this.url + 'me/', options))
);
}
// try 2 : Doesn't work either
getAllLiabilities(): Observable<Liability[]> {
return this.authService.getOptions()
.pipe(
switchMap(options => this.http.get<Liability[]>(this.url + 'me/', options)), // at this point I tried pretty much every operators (map, mergeMap etc.)
withLatestFrom()
);
}
/* this code was working before that I transformed the authService.getOptions in observable (it was just returning the options synchronyously before)
getAllLiabilities(): Observable<Liability[]> {
return this.http.get<Liability[]>(this.url + 'me/', this.authService.getOptions());
}*/
}
授權服務.ts
public getOptions(): Observable<any> {
return new Observable((observer) => {
this.storage.get('authToken').then((token) => {
console.log('passing') // Pass here
if (token && typeof token.auth_token !== 'undefined') {
console.log('passing') // pass here as well
this.isLoggedIn = true;
this.token = token.auth_token;
}
// it is returning the value
return {
headers: this.headers.set('Authorization', 'Bearer ' + this.token),
params: new HttpParams()
};
})
});
}
我嘗試了幾乎所有可能的運算符組合以使其在 liabilityService 中工作但沒有成功。
問題是我的page.ts
訂閱了this.http.get<Liability[]>(this.url + 'me/', options)
觀察者,但沒有觸發 xhr 請求。 http get observer 永遠不會執行,我不明白我在那里遺漏了什么。
我剛剛開始試驗 Angular,但如果我理解正確,操作員應該進行映射和展平,但這看起來永遠不會發生。
我不明白為什么初始代碼:
return this.http.get<Liability[]>(this.url + 'me/', this.authService.getOptions());
正在返回一個Observable<Liability[]>
並使用 switchMap:
switchMap(options => this.http.get<Liability[]>(this.url + 'me/', options))
它返回一個Observable<HttpEvent<Liability[]>>
如果有人有線索並有時間回答我,那就太棒了
您在 promise 回調then()
中遇到問題:
this.storage.get('authToken').then((token) => {
return something; // this won't work.
})
相反,您可以使用from
,它將您的 promise convert
為可觀察的。
import { from, Observable } from 'rxjs';
import { map } from 'rxjs/operators';
public getOptions(): Observable<any> {
return from(this.storage.get('authToken')).pipe(map(token => {
return headers with token.
}));
}
所以你可以像這樣重寫你的代碼:
授權服務:
private token: string | null = null;
public getOptions(): Observable<any> {
return this.getToken().pipe(
map(token => {
return {
headers: this.headers.set('Authorization', 'Bearer ' + token),
params: new HttpParams()
};
})
);
}
private getToken(): Observable<string | null> {
if (this.token) {
return of(this.token);
}
return from(this.storage.get('authToken')).pipe(
map(token => token?.authToken || null),
tap(token => this.token = token)
);
}
然后你可以使用開關圖:
getAllLiabilities(): Observable<Liability[]> {
return this.authService.getOptions().pipe(
switchMap(options => this.http.get<Liability[]>(this.url + 'me/', options))
);
}
獲取HttpEvent<T>
的原因是因為當.get()
的重載接收到any
object 時,它會將 http 事件處理完全交給您。 如果你想讓它返回提供的元素類型,你必須滿足適當的重載。 你可以這樣做:
我們沒有返回整個選項,而是只返回標頭,這應該足夠了,因為我們真的沒有足夠的東西來說明選項的 rest。
授權服務
private token: string | null = null;
public createTokenHeaders(): Observable<HttpHeaders> {
const headers = new HttpHeaders();
return addToken(headers);
}
public addToken(headers: HttpHeaders): Observable<HttpHeaders> {
return this.getToken().pipe(
map(token => headers.set('Authorization', 'Bearer ' + (token || '')))
);
}
private getToken(): Observable<string | null> {
if (this.token) {
return of(this.token);
}
return from(this.storage.get('authToken')).pipe(
map(token => token?.authToken || null),
tap(token => this.token = token)
);
}
然后像這樣使用它:
getAllLiabilities(): Observable<Liability[]> {
const url = this.url + 'me/';
const headers = new HttpHeaders();
return this.authService.addToken(headers).pipe(
switchMap(updatedHeaders => this.http.get<Liability[]>(url, { headers: updatedHeaders }))
);
}
要么:
getAllLiabilities(): Observable<Liability[]> {
const url = this.url + 'me/';
return this.authService.createTokenHeaders().pipe(
switchMap(headers => this.http.get<Liability[]>(url, { headers }))
);
}
注意:確保使用從調用 addToken 返回的標頭。 重用您自己的實例化headers
將不起作用,因為設置 header 總是會返回一個新的HttpHeaders
object。它是不可變的。
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