Angular 5：无法读取未定义的属性“订阅”

Question

我已经尝试了很多天来解决 stackoverflow 上的这个错误，因为我现在是 Angular 的新手，所以我只需要向社区询问。我一直在研究 JWT 身份验证

错误类型错误：无法读取未定义的属性“订阅” 在 RawMaterialComponent.loadRawMaterialsByCompany (raw-material.component.ts:774)

我在组件中有如下服务调用

    private loadRawMaterialsByCompany(callback: any) {
    let serviceSubscriptions =this.rawMaterialService.getRawMaterialsByCompany().subscribe(data => {
      this.rawMaterials = data;
      this.rawMaterialLoading = false;
    }, 
     error => this.handleError(error));
    }

服务如下

     getRawMaterialsByCompany() {
        const url = this.raw_material_api_endpoint + 'Company/' + this.company_id;
        return this.get(url);
      }

上面的服务调用重定向到基础服务，它实现了所有的http请求，即：get、post

我在这里要做的是，如果访问令牌已过期，我想刷新令牌。使用发布请求

     protected get(url: string) {
        if (this.isTokenExpired(localStorage.getItem('userToken'))) {

            this.getOriginalDataset(url).then((val)=>{

            this.getTokenfromService()
            return(val)
          });
        } else {
          return this.http.get(url)
            .map(this.extractRequests)
            .catch(this.handleError);
        }


    protected post(url: string, body: any) {
        if (url.includes("RefreshToken") || url.includes("Login") || url.includes("Logout")) {
          return this.http.post(url, body, { headers: this.getHeaders() })
            .map(this.extractRequests)
            .catch(this.handleError);
        }
        else {
            return this.http.post(url, body, { headers: this.getHeaders() })
              .map(this.extractRequests)
              .catch(this.handleError);

        }

      }

**现在我不会为发布请求刷新令牌

getOriginalDataset() 方法为原材料组件带来请求的数据

getTokenfromService() 方法获取新的访问令牌和刷新令牌存储在本地存储中

    sendoriginalDataset(originalUrl):Promise<any>{
        return new Promise(resolve => {
        const dataSet= this.http.get(originalUrl, { headers: this.getHeaders() })
        .map(this.extractRequests)
        .catch(this.handleError);
        resolve(dataSet)
        });
      }

    async getTokenfromService() {

        const base64EncodedJwtAndRefreshToken = btoa(encodeURI(`${localStorage.getItem('userToken')}:${localStorage.getItem('refreshToken')}`));
        const url = this.login_api_endpoints + 'RefreshToken/';
        this.asyncResult = await this.post(url, JSON.stringify(base64EncodedJwtAndRefreshToken))
          .toPromise();
        console.log('First Promise resolved.')
        if (this.asyncResult !== null) {
          localStorage.setItem('userToken', this.asyncResult.jwtToken)
          localStorage.setItem('refreshToken', this.asyncResult.refreshToken)

        }

      }

两种方法都运行正常，但是一旦 getTokenfromService() 执行发布请求，控制台错误就会弹出 Cannot read property 'subscribe' of undefined

每个 http 请求都会发生这种情况，上面是一个示例。非常感谢您的小帮助！

Answer 1

您不能subscribe 承诺。变化：

this.getOriginalDataset(url).then((val)=>{
this.getTokenfromService()
return(val)

收件人：

return from(this.getOriginalDataset(url)).pipe(
  tap(() => this.getTokenfromService())
)

Answer 2

你必须使用 await 来获取数据

await this.getTokenfromService()

如果还有错误请告诉我