import {
  HttpHandler,
  HttpInterceptor,
  HttpParams,
  HttpRequest,
} from '@angular/common/http';
import { Injectable } from '@angular/core';
import { exhaustMap, take } from 'rxjs/operators';
import { AuthenticationService } from './authentication.service';

@Injectable()
export class AuthInterceptorService implements HttpInterceptor {
  constructor(private authService: AuthenticationService) { }

  intercept(req: HttpRequest<any>, next: HttpHandler) {
    return this.authService.emitUser.pipe(
      take(1),
      exhaustMap((user) => {
        if (!user) {
          return next.handle(req);
        }
        const modifiedReq = req.clone({
          params: new HttpParams().set('auth', user!.token!),
        });

        return next.handle(modifiedReq);
      })
    );
  }
}

这是一个拦截器文件，它通过添加'auth'查询参数和一个值来修改请求URL，该值作为我们从这里的user对象获得的令牌。但我不明白exhaustMap里面发生了什么。