使用forkjoin合并http observable

问题描述

我试图通过使用 forkjoin 来避免嵌套的observable。当前（嵌套）版本如下所示：

I'm trying to avoid nested observables by using forkjoin. The current (nested) version looks like this:

  this.http.get('https://testdb1.firebaseio.com/.json').map(res => res.json()).subscribe(data_changes => {
    this.http.get('https://testdb2.firebaseio.com/.json').map(res => res.json()).subscribe(data_all => {
      /* Do this once resolved */
      this.platform.ready().then(() => {
        this.storage.set('data_changes', data_changes);
        this.storage.set('data_all', data_all);
        document.getElementById("chart").innerHTML = "";
        this.createChart();
      });
    });
  },

    err => {
      this.platform.ready().then(() => {
        console.log("server error 2");
        document.getElementById("chart").innerHTML = "";
        this.createChart();
      });
    });
  }

我可以将第一部分重写为：

I can rewrite the first part as:

Observable.forkJoin(
  this.http.get('https://testdb1.firebaseio.com/.json').map((res: Response) => res.json()),
  this.http.get('https://testdb2.firebaseio.com/.json').map((res: Response) => res.json())
)

但我不确定如何添加 .subscribe 方法访问 data_changes 和 data_all 。

But i'm not sure how I would then add the .subscribe method to access both data_changes and data_all.

再看另一个例子，我知道它应该看起来像 .subscribe（res => this.combined = {friends：res [0 ] .friends，customer：res [1]}）; ，但我不知道如何将其改编为我的例子。

Looking at another example, I know it should look something like .subscribe(res => this.combined = {friends:res[0].friends, customer:res[1]});, but i'm not sure how to adapt this to my example.

推荐答案

尝试使用 combineLatest 而不是 forkJoin ：

使用 combineLatest ：

With combineLatest :

const combined = Observable.combineLatest(
  this.http.get('https://testdb1.firebaseio.com/.json').map((res: Response) => res.json()),
  this.http.get('https://testdb2.firebaseio.com/.json').map((res: Response) => res.json())
)

combined.subscribe(latestValues => {
    const [ data_changes , data_all ] = latestValues;
    console.log( "data_changes" , data_changes);
    console.log( "data_all" , data_all);
});

您也可以通过forkJoin处理它，但forkJoin将在所有调用完成后返回数据并返回结果，但在combineLatest当任何observable发出一个值时，从每个值发出最新值。

You can also handle it by forkJoin , but forkJoin will return data when all calls are finished and return result , but in combineLatest When any observable emits a value, emit the latest value from each.

使用 forkJoin ：

With forkJoin :

const combined = Observable.forkJoin(
  this.http.get('https://testdb1.firebaseio.com/.json').map((res: Response) => res.json()),
  this.http.get('https://testdb2.firebaseio.com/.json').map((res: Response) => res.json())
)

combined.subscribe(latestValues => {
    const [ data_changes , data_all ] = latestValues;
    console.log( "data_changes" , data_changes);
    console.log( "data_all" , data_all);
});

调用两个并检查控制台日志，你会明白的。

Call both and check the console log , you will get idea.

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