Angularfire2如何处理安古拉4-5中的多个观测数据

Question

在执行一个函数之前，从多个可观察到的数据中获取数据的最佳方法是什么？

例子：

provider.ts

obs1 = this.afDB.object(`app/radio`).snapshotChanges();
obs2 = this.afDB.object(`app/users`).snapshotChanges();
obs3 = this.afDB.object(`app/song`).snapshotChanges();

app.ts

doSomething(){

console.log('this is my', ${radio}, 'it plays on this date:' ,${date}, 'this song', ${song}`);

}

我把订阅放在一起..。很管用，但是..。处理这种异步行为的正确方法是什么？

doSomething(){

provider.obs1.subscribe(val1 =>{
provider.obs2.subscribe(val2 =>{
provider.obs3.subscribe(val3 =>{

 console.log('this is my', ${val1.payload.val().radio}, 'it plays on this date:' ,${val2.payload.val().date}, 'this song', ${val3.payload.val().song}`);

});
});
});

    }

Answer 1

使用forkJoin运算符。

doSomething(){
   Observable.forkJoin(
      provider.obs1,
      provider.obs2,
      provider.obs3
   ).subscribe(data => {
       console.log("values: ",data[0], data[1], data[2]) 
   }, err => {
       console.log("Handle error here");
   })
}