angular - 无法解析 AuthenticationService : ([object Object], 的所有参数？，[object Object])

Question

我遇到了下一个错误，无法理解如何解决它。

Can't resolve all parameters for AuthenticationService: ([object Object], ?, [object Object])

我几乎检查了这里的每个主题，并尝试了多种方法来解决它，但第二天仍然无法解决。

我试过像这样在 appService 中注入(inject)第一个 authService 但得到同样的错误

@Inject(forwardRef(() => AuthenticationService)) public authService: AuthenticationService

我已经检查了服务中的所有 DI 和导入顺序，在我看来一切都是正确的

所以，如果有人可以帮助我处理它，我将不胜感激。

Angular 4.0.0

授权服务

    import { Injectable } from '@angular/core';
import {Http, Headers, Response} from '@angular/http';
import 'rxjs/add/operator/toPromise';
import {Observable} from 'rxjs/Rx';

import {AppServices} from "../../app.services";
import {Router} from "@angular/router";

@Injectable()
export class AuthenticationService {
  public token: any;

  constructor(
    private http: Http,
    private appService: AppServices,
    private router: Router
  ) {
    this.token = localStorage.getItem('token');
  }

  login(username: string, password: string): Observable<boolean> {
    let headers = new Headers();
    let body = null;
    headers.append("Authorization",("Basic " + btoa(username + ':' + password)));

    return this.http.post(this.appService.api + '/login', body, {headers: headers})
      .map((response: Response) => {
        let token = response.json() && response.json().token;
        if (token) {
          this.token = token;
          localStorage.setItem('Conform_token', token);
          return true;
        } else {
          return false;
        }
      });
  }

  logout(): void {
    this.token = null;
    localStorage.removeItem('Conform_token');
    this.router.navigate(['/login']);
  }
}

应用服务

import {Injectable} from '@angular/core';
import {Headers, Http, RequestOptions} from '@angular/http';
import {Router} from "@angular/router";
import {AuthenticationService} from "./auth/auth.service";

import 'rxjs/add/operator/toPromise';
import {Observable} from 'rxjs/Rx';

@Injectable()

export class AppServices {

  api = '//endpoint/';

  public options: any;
  constructor(
    private http: Http,
    private router: Router,
    public authService: AuthenticationService // doesn't work
  //  @Inject(forwardRef(() => AuthenticationService)) public authService: AuthenticationService // doesn't work either
      ) {
        let head = new Headers({
      'Authorization': 'Bearer ' + this.authService.token,
      "Content-Type": "application/json; charset=utf8"
    });
    this.options = new RequestOptions({headers: head});
  }

  // ====================
  //    data services
  // ====================

  getData(): Promise<any> {
    return this.http
      .get(this.api + "/data", this.options)
      .toPromise()
      .then(response => response.json() as Array<Object>)
      .catch((err)=>{this.handleError(err);})
  }

应用模块

import { BrowserModule } from '@angular/platform-browser';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import {BaseRequestOptions, HttpModule} from '@angular/http';

import { MaterialModule} from '@angular/material';
import {FlexLayoutModule} from "@angular/flex-layout";
import 'hammerjs';

import { routing, appRoutingProviders }  from './app.routing';
import { AppServices } from './app.services';
import {AuthGuard} from "./auth/auth.guard";
import {AuthenticationService} from "./auth/auth.service";

import {AppComponent} from './app.component';
import {AuthComponent} from './auth/auth.component';
import {NotFoundComponent} from './404/not-found.component';
import { HomeComponent } from './home/home.component';

@NgModule({
  declarations: [
    AppComponent,
    AuthComponent,
    NotFoundComponent,
    HomeComponent
  ],
  imports: [
    BrowserModule,
    BrowserAnimationsModule,
    FormsModule,
    HttpModule,
    routing,
    MaterialModule,
    FlexLayoutModule
  ],
  providers: [AppServices, AuthGuard, AuthenticationService],
  bootstrap: [AppComponent]
})
export class AppModule { }

Answer 1

您在 AppServices 和 AuthenticationService 之间存在循环依赖 - 这对于 Angular 使用的构造函数注入(inject)是不可能的。

要变通，您可以使用

export class AuthenticationService {
  public token: any;
  appService: AppServices;
  constructor(
    private http: Http,
    // private appService: AppServices,
    injector:Injector;
    private router: Router
  ) {
    setTimeout(() => this.appService = injector.get(AppServices));
    this.token = localStorage.getItem('token');
  }

另见 DI with cyclic dependency with custom HTTP and ConfigService

要避免 setTimeout，您还可以从 AppService 的构造函数中设置 AuthenticationService.appService(或相反)