[英]Rxjs Nested observer is not executed
I've read a lot of documentation, articles and different thread about how to nest observers in RxJs and Angular, I still missing something and not able to get a result at the end.我已经阅读了很多关于如何在 RxJs 和 Angular 中嵌套观察者的文档、文章和不同的线程,但我仍然遗漏了一些东西并且最终无法得到结果。
page.ts页面.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 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());
}*/
}
auth.service.ts授权服务.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()
};
})
});
}
I tried almost all the possible operator combinations to make it works in the liabilityService without any success.我尝试了几乎所有可能的运算符组合以使其在 liabilityService 中工作但没有成功。
The problem is that my page.ts
subscribes to the this.http.get<Liability[]>(this.url + 'me/', options)
observer but none xhr request is fired.问题是我的
page.ts
订阅了this.http.get<Liability[]>(this.url + 'me/', options)
观察者,但没有触发 xhr 请求。 The http get observer is never executed and I don't understand what I'm missing there. http get observer 永远不会执行,我不明白我在那里遗漏了什么。
I'm just starting experimenting Angular, but if I understood correctly the operators should do the mapping and flattening but this looks to never happen.我刚刚开始试验 Angular,但如果我理解正确,操作员应该进行映射和展平,但这看起来永远不会发生。
I'm not catching either why the initial code:我不明白为什么初始代码:
return this.http.get<Liability[]>(this.url + 'me/', this.authService.getOptions());
is returning an Observable<Liability[]>
正在返回一个
Observable<Liability[]>
and with the switchMap:并使用 switchMap:
switchMap(options => this.http.get<Liability[]>(this.url + 'me/', options))
It is returning a Observable<HttpEvent<Liability[]>>
它返回一个
Observable<HttpEvent<Liability[]>>
If somebody has a clue and the time to answer me on that, it would be amazing如果有人有线索并有时间回答我,那就太棒了
You have a problem in the promise callback then()
:您在 promise 回调
then()
中遇到问题:
this.storage.get('authToken').then((token) => {
return something; // this won't work.
})
instead you can use from
, which will convert
your promise to an observable.相反,您可以使用
from
,它将您的 promise convert
为可观察的。
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.
}));
}
So you could rewrite your code like this:所以你可以像这样重写你的代码:
auth service:授权服务:
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)
);
}
then you can use a switchmap:然后你可以使用开关图:
getAllLiabilities(): Observable<Liability[]> {
return this.authService.getOptions().pipe(
switchMap(options => this.http.get<Liability[]>(this.url + 'me/', options))
);
}
The reason for getting HttpEvent<T>
is because when the overload of .get()
receives an any
object it leaves the http event handling entirely up to you.获取
HttpEvent<T>
的原因是因为当.get()
的重载接收到any
object 时,它会将 http 事件处理完全交给您。 If you want it to return the provided element type, you have to satisfy the proper overload.如果你想让它返回提供的元素类型,你必须满足适当的重载。 You can achieve that doing it like so:
你可以这样做:
Instead of returning the entire options, we only return the headers, which should be enough, because we do not really have enough to say about the rest of the options.我们没有返回整个选项,而是只返回标头,这应该足够了,因为我们真的没有足够的东西来说明选项的 rest。
auth service授权服务
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)
);
}
Then use it like so:然后像这样使用它:
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 }))
);
}
or:要么:
getAllLiabilities(): Observable<Liability[]> {
const url = this.url + 'me/';
return this.authService.createTokenHeaders().pipe(
switchMap(headers => this.http.get<Liability[]>(url, { headers }))
);
}
Note: Make sure you use the headers returned from the call to addToken.注意:确保使用从调用 addToken 返回的标头。 Reusing your own instantiated
headers
will not work because setting a header always returns a new HttpHeaders
object. It is immutable.重用您自己的实例化
headers
将不起作用,因为设置 header 总是会返回一个新的HttpHeaders
object。它是不可变的。
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