在 Angular HttpClient 拦截器中使用承诺

Question

我可以在HttpInterceptor 中使用promise 吗？例如：

export class AuthInterceptor implements HttpInterceptor{
this.someService.someFunction()
    .then((data)=>{
       //do something with data and then
       return next.handle(req);
    });
}

为什么我需要这个？因为在向服务器发出请求之前，我需要获取一个令牌以添加到请求标头中。

我的拦截器：

@Injectable()
export class AuthInterceptor implements HttpInterceptor{

    constructor(private authService: AuthService){}

    intercept(req: HttpRequest<any>, next: HttpHandler) : Observable<HttpEvent<any>>{
        console.log('Intercepted!');
        // return next.handle(req);
        this.authService.getToken()
            .then((token)=>{
                console.log(token);
                const reqClone = req.clone({
                    headers: req.headers
                            .set('Authorization', 'Bearer ' + token)
                            .append('Content-Type', 'application/json')
                });
                console.log(reqClone);
                return next.handle(reqClone);
            })
            .catch((err)=>{
                console.log('error in interceptor' + err);
                return null;
            });
    }
}

请求：

this.http.post(this.baseURL + 'hero', data)
                    .subscribe(
                            (res: any) => {
                                console.log('Saved Successfully.');
                                console.log(res);
                            },
                            (err: any) => {
                                console.log('Save Error.' + err);
                            }
                        );

我面临的问题：

->我在承诺解决之前收到此错误。

You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.

承诺兑现，我得到了我的令牌，但在错误发生之后。

Answer 1

更新：使用 rxjs@6.x

import { from, Observable } from 'rxjs';
import { switchMap } from 'rxjs/operators';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {

    constructor(private authService: AuthService){}

    intercept(request: HttpRequest<any>, next: HttpHandler) : Observable<HttpEvent<any>>{
        return from(this.authService.getToken())
              .pipe(
                switchMap(token => {
                   const headers = request.headers
                            .set('Authorization', 'Bearer ' + token)
                            .append('Content-Type', 'application/json');
                   const requestClone = request.clone({
                     headers 
                    });
                  return next.handle(requestClone);
                })
               );
    }
}

原始答案

是的，你可以将需要的服务注入到拦截器的构造方法中，并在intercept的实现中检索值，创建一个新的更新的http请求并处理它。

我不擅长承诺，所以你可以尝试以下方法：

import { fromPromise } from 'rxjs/observable/fromPromise';

@Injectable()
export class AuthInterceptor implements HttpInterceptor{

    constructor(private authService: AuthService){}

    intercept(req: HttpRequest<any>, next: HttpHandler) : Observable<HttpEvent<any>>{
        return fromPromise(this.authService.getToken())
              .switchMap(token => {
                   const headers = req.headers
                            .set('Authorization', 'Bearer ' + token)
                            .append('Content-Type', 'application/json');
                   const reqClone = req.clone({
                     headers 
                    });
                  return next.handle(reqClone);
             });
    }
}

Answer 2

对于 RxJS 6+，我更新了 Jota.Toledo 的答案：

import { fromPromise } from 'rxjs/observable/fromPromise';

@Injectable()
export class AuthInterceptor implements HttpInterceptor{
constructor(private authService: AuthService){}
intercept(req: HttpRequest<any>, next: HttpHandler) : Observable<HttpEvent<any>>{
    return fromPromise(this.authService.getToken())
          .pipe(switchMap(token => {
               const headers = req.headers
                        .set('Authorization', 'Bearer ' + token)
                        .append('Content-Type', 'application/json');
               const reqClone = req.clone({
                 headers 
                });
              return next.handle(reqClone);
         }));
 }  
}

Answer 3

轮到我了（感谢 Jota.Toledo 和 Capripio）：

1) 将 "fromPromise" 切换为 "from" --> fromPromise does not exist on type Observable

2) 修复 'application/json' 引用

import { Observable, from } from 'rxjs';
import { switchMap } from 'rxjs/operators';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {

  constructor(private authService: AuthService){}

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

      return from(this.authService.getToken()).pipe(
        switchMap(token => {
            const headers = req.headers
                .set('Authorization', 'Bearer ' + token)
                .append('Content-Type', 'application/json');
            const reqClone = req.clone({
                headers
            });
            return next.handle(reqClone);
        }));
   }
}

我的 RxJs 版本：“6.2.2” 希望对您有所帮助！