Question

我有一项服务，该服务扩展了用于处理错误数据的基本服务。

例如

import { CurrentUserService } from './current-user.service';
import { CONFIG } from './../shared/base-urls';
import { BaseServiceService } from './base-service.service';
import { Injectable } from '@angular/core';
import { Http, Headers, Response, RequestOptions, ResponseContentType } from '@angular/http';
import { Router } from '@angular/router';

let baseUrl = CONFIG.baseUrls.url;

@Injectable()
export class ChildService extends BaseServiceService {

   constructor(
      public _http: Http,
      public _currentUser: CurrentUserService, 
      public _router: Router) 
   {
      super(_router, _http, _currentUser);
   }

   getFaqData() {
      var headers = new Headers();
      this.token = this._currentUser.getProfile().token;
      let sessionId = this._currentUser.getProfile().sessionId;
      headers.append('Authorization', `Bearer ${this.token}`);
      headers.append('Content-Type', 'application/json; charset=utf-8');
      return this._http.get(baseUrl + "api/UserAdmin/GetFaq", { headers: headers })
         .map((response: Response) => response.json())
         .catch(this.handleError)
   }
}

当位于基本服务中时发生错误this.handleError时，但是例如在401错误时尝试使用基本服务中的实例重定向用户时，则基本服务中的引用为null。

请参见下文，获取错误cannot read the property 'navigate' of undefined

   //Inside BaseServiceService 

   constructor(
      public _router: Router, 
      public _http: Http, 
      public _currentUser: CurrentUserService) 
   {}

   protected handleError(response: Response):any {
      var message = "";
      if (response.status == 401) {  
        //cannot read the property 'navigate' of undefined   
        this._router.navigate(["/login", false]);
      }
      return Observable.throw(message || 'We apologise. There was a technical error processing the request. Please try again later.')
   }

我该如何纠正？

Answer 1

您有一个此参考问题，当您在catch函数中传递一个函数时，此不再引用该对象，您必须使用箭头函数，并在其中调用handleError，

catch((err)=>this.handleError(err)) //it will save the context

或使用绑定方法

   catch(this.handleError.bind(this)) it will do the same

尝试处理错误时未定义基本服务，角度

1 个答案: