问题描述：

我需要发出2个http请求(第二个依赖于第一个)，以将用户凭据插入我的数据库.

i need to make 2 http request (the second dependent on the first) to insert user credentiels into my data base.

第一个服务获取用户凭据( http://localhost: 55978/FleetViewDBWebService.asmx/ChekCreds?name = name1& subname = subname1 )，然后检查该用户是否已经存在，返回"ID"(如果存在)，或者返回"ok"(如果该用户不存在)

the first service get the user credentiels (http://localhost:55978/FleetViewDBWebService.asmx/ChekCreds?name=name1&subname=subname1) and check if the user already exist or not, return the 'ID' if it exist , or "ok" if the user doesn't exist.

然后，我需要订阅第一个服务并获得返回的值. 如果确定"，请调用第二个服务( http://本地主机:55978/FleetViewDBWebService.asmx/InsertUser?name = name1& subname = subname1& Telephone = 334580021 )
插入用户凭证，否则返回任何消息.

then i need to subscribe to the first service and get the returned value. if "ok" call the second service (http://localhost:55978/FleetViewDBWebService.asmx/InsertUser?name=name1&subname=subname1&Telephone=334580021)
to insert the user credentiels , else return any message .

我打电话给第一个服务并得到结果，但是我不知道如何添加第二个服务.

I call the first service and get the result but i have no idea how to add the second service.

有什么想法

CheckCreds(value: any) {
    let headers = new Headers({ 'Content-Type': 'application/json' });
    let options = new RequestOptions({ headers: headers });

    let params = new URLSearchParams();



    params.set('name', (value.nom).toString());
    params.set('subname', (value.prenom).toString());

    return this.http.get(this.checkUri, {
        search: params, withCredentials: true
    })
        .map(res => {
            console.log("++++" + res.text());


            return JSON.parse(res.text());
        })
        .catch(this.handleError)


}

component.ts

 submitForm($ev, value: any) {
    $ev.preventDefault();
    for (let c in this.valForm.controls) {
        this.valForm.controls[c].markAsTouched();
    }
    if (this.valForm.valid) {
        this.Service.CheckCreds(value)
            .subscribe(
            res => {
                string result=JSON.stringify(res);
            },
            e => {
                alert(e);
            },
            () => {
            }

            );

    }
}

答

RxJS方法是使用

The RxJS way would be to use the switchMap operator to wait for the response of the first request to arrive before firing the second request.

return this.http.get('url/1')
  .switchMap(res1 => {
    // use res1 to further control param of the second call
    this.http.get('url/2')
  })
  .subscribe(res2 => {
    //do stuff with the second response
  })

要并行执行请求(对于彼此不依赖的请求)，请使用

To do the requests in parallel (for requests which are not dependant of one another), use the forkJoin static operator.

return Observable.forkJoin(
  this.http.get('url/1'),
  this.http.get('url/2'),
)
  .subscribe(([res1, res2]) => {
    // res1 and res2 available after both requests are completed
  })

如何在Angular 2中进行2个依赖的http请求

component.ts

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