Angular 8 异步调用未等待 promise 完成且结果为错误请求

Question

我希望我的异步调用在完成之前不要转到下一个语句，但它仍在继续并且在请求完成后它会导致错误作为错误请求，即使 url 路径和 http headers 是 correct.if 我使用 observable 和 subscribe 的工作方式来完成它但是在完成请求之前转到下一个语句，所以我认为 promise async/await 可以帮助但是我做错了什么，任何帮助是非常可观。这是我的代码。

myapp.service.ts

//Because we are not using a type checker, so the response should be extracted. Add this function after the constructor for extract it.
private extractData(res: Response) {
    let body = res;
    return body || {};
  }
private handleError(error) {
    return throwError(error);
  }
async getEntityDependencies(entitytype: string) {
    try {      
      var authheader = { headers: new HttpHeaders({ 'accesstoken': this.accesstoken, 'Content-Type': 'application/json', })};

      return await this.http.get(this.endpoint, authheader).pipe(map(this.extractData), catchError(this.handleError)).toPromise();       
    } 
    catch (error) {
      console.log(error);
    }
  }

newform.component.ts

async CreateForm() {
  // const data = await this.rest.getEntityDependencies(this.dataservice.entitytype)
  await this.rest.getEntityDependencies(this.dataservice.entitytype).then((data: {}) => { // data is getting undefined since request results Bad request
    // my stuff using data...
  }, error => {
    console.log(error, "Error from API");
  });
}

Answer 1

代码中有两个问题

首先你不需要 return await

async getEntityDependencies(entitytype: string) {
    try {      
      var authheader = { headers: new HttpHeaders({ 'accesstoken': this.accesstoken, 'Content-Type': 'application/json', })};

      return this.http.get(this.endpoint, authheader)
         .pipe(
            map(this.extractData), 
            tap(data => console.log('data in service', data))
            catchError(this.handleError)
         ).toPromise();       
    } 
    catch (error) {
      console.log(error);
    }
  }

第二种方法

async CreateForm() {
  try
  {
     const data = await this.rest.getEntityDependencies(this.dataservice.entitytype);
     console.log('data', data);
  }
  catch(ex) {
     console.error(ex);
  }
}

Angular 8 异步调用未等待 promise 完成且结果为错误请求

Angular 8 Async call not waiting for promise to complete and results as bad request

typescript

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angular8

angular-promise