rxjs从第二个请求返回值

Question

我从第二个请求返回Observable时出现问题。 事情是这样的：

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，从第一.MAP的commandRequest返回值（）。如果我试图从内部订阅compiller抛出错误返回值： [ts]声明类型既不是'无效'也不是'任何'的函数必须返回一个值。 https://habrastorage.org/web/93b/e6b/17b/93be6b17bf5b46b5847e67deefd6eea1.png

Answer 1

从一个流映射到另一个可以使用mergeMap或switchMap

commandRequest(action:string, commandData:any):Observable<CashDesckResponse> 
{ 
    return this.requestCommandString(action, commandData, "POST") 
     .map(r1 => new CashDesckRequest(r1.response) 
     // map first response to command instance 
     .mergeMap(command =>this.server.executeCommand(command)); 
     // map the command observable to a new observable 
}