angular - 异步 API 调用问题：迭代第一个响应并传递值以在 Angular 6 中进行另一个 API 调用

Question

我是 java 开发人员，尝试使用需要同步调用的异步 API 调用。我需要进行第一个 API 调用 >> 将响应迭代为数组 >> 进行另一个 API 调用 >> 返回最后一个 API 调用的响应并订阅它

以前，我使用 switchmap 实现了多个 API 调用，但不知道如何在迭代中使用 switchmap 或其他任何东西。

这是我的代码

multipleAction(actionServiceName,host,hanger,toDoAction) {
 .........       

    let getServiceUrl = `/${proxy}/services/${actionHostName}/`;

    if(toDoAction=="stopservice"){
            return this.http.get(getServiceUrl,httpOptions)
    .pipe(map((output:Response) => { 
            let array = JSON.parse(JSON.stringify(output));
            array.forEach(element => {
                if(element.serviceName==actionServiceName && element.status=="Up")
                {
                    console.log("stopping service");
         // Here is issue. Trying to achieve something like this, being backend developer. i know this API call doesnt work in Angular
                    let res = this.startStopService(proxy,toDoAction,actionHostName,actionServiceName,element.serviceVersion,httpOptions);
                    console.log("step 2:",res);
                 //need this value to be subscribed
                    return res;
                }
            });
        }));
        }         
}

及其他功能

startStopService(proxy,toDoAction,actionHostName,actionServiceName,serviceVersion,httpOptions){ 

    let getStatusUrl = `/${proxy}/servicestatus/${actionHostName}/${actionServiceName}/CSS/${serviceVersion}`;
    let serviceActionUrl = `/${proxy}/${toDoAction}/${actionHostName}/${actionServiceName}/CSS/${serviceVersion}`;

//these two API calls works fine this function is called separately. but doesnt work synchronously when with previous function

    return this.http.get(getStatusUrl,httpOptions)
    .pipe(map((output) => { 
        return output;
    }),
    switchMap(output =>
    this.http.get(serviceActionUrl
    +JSON.parse(JSON.stringify(output)).statusDescription,
    httpOptions)),        
    tap(output2 => {  
        console.log(JSON.parse(JSON.stringify(output2)).statusDescription);
    }))
}

Answer 1

你需要的是一个concatMap。

“concatMap 在前一个完成之前不会订阅下一个 observable”

请参阅此内容以供参考。