rxjs从第二个请求返回值

类似这样:

commandRequest(action:string, commandData:any):Observable<CashDesckResponse>
{
    let command:CashDeskRequest;
    //ask my backend for command
    this.requestCommandString(action, commandData, "POST")
        //this is my response from backend
        .map(r=>r.response).subscribe(my_1_response=>{
        //then i need to send this response data to other server/action 
        //to execute it and return this second response as the result of
        //this method.
        command = new CashDesckRequest(my_1_response);
        return this.server.executeCommand(command).map(return_this=>return_this);
    }); 
};

private requestCommandString(action:string, requestData:any,
                             type:string):Observable<AjaxResponse>{
    return Observable.ajax({
        body:JSON.stringify(requestData),
        method:type,
        url:this._apiServerUrl+action
    }).map(r=>r);
};

我的问题是commandRequest从第一个返回值。map()。如果我尝试从内部订阅编译器返回值,则抛出错误: [ts]声明类型既不是“void”也不是“any”的函数必须返回值。 https://habrastorage.org/web/93b/e6b/17b/93be6b17bf5b46b5847e67deefd6eea1.png