订阅流后如何返回数据？答案

【问题标题】：How to return data after stream was subscribed?订阅流后如何返回数据？
【发布时间】：2019-01-10 06:59:27
【问题描述】：

订阅流后如何返回数据？比如我在订阅中获取URL，然后我想根据这个URD返回带有数据的流

public get() {
    this.service.getData().subscribe((data: any) => {
        // data was setted here
        this.url = data;
    });

    return this.http.get(this.url)
        .map(r => {
            ...
            return obj;
        });
}

【问题讨论】：

标签： angular typescript rxjs subscription

【解决方案1】：

您应该为此使用concatMap（或mergeMap）并将其变成一个链：

public get() {
  this.service.getData().do((data: any) => {
      // data was set here
      this.url = data;
    })
   .concatMap(data => this.http.get(data))
   .map(r => {
     ...
     return obj;
    });
}

或者你甚至不需要使用this.url（我不知道你的用例是什么）。

public get() {
  this.service.getData()
   .concatMap(url => this.http.get(url))
   .map(r => {
     ...
     return obj;
    });
}

【讨论】：

【解决方案2】：

this.service.getData().subscribe((data: any) => {
  // data was setted here
  return this.http.get(data)
  .map(r => {

    return r;
  });
});

或

     public get() {
        this.service.getData().subscribe((data: any) => {
        // data was setted here
        this.url = data;
        this.get2(this.url);
        });
}
public get2(url){
     return this.http.get(url)
      .map(r => {
        ...
        return obj;
      });
}

【讨论】：

【解决方案3】：

尝试：

public get() {
        this.service.getData().subscribe((data: any) => {
        // data was setted here
        this.url = data;

        //get data with the URL
        return this.http.get(data)
            .map(r => {
                //Get something with data obtained with the URL
                return obj;
              });
        });
      }

【讨论】：