使用forkjoin合并http observable

Question

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

  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:

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())
)

但我不知道如何添加.subscribe方法来访问data_changes和data_all.

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]});,但我不知道如何适应我的例子.

Answer 1

尝试使用combineLatest而不是forkJoin:

用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将在所有调用完成并返回结果时返回数据,但在combineLatest中当任何observable发出值时,从每个调用发出最新值.

用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.