Efficiently get Observable of an array BehaviorSubjects

问题

I have this field:

smartArray: BehaviorSubject<BehaviorSubject<object>[]>; 
//Example
[{key1: 'value1', key2: value2},...]; 

I now want to get and subscribe to one of the properties:

getObeservablePropertyOfSmartArray(index, property){
   return this.smartArray.pipe(
         //...getelementAtIndex <---dont know how
         //lets say the elementatIndex is elem: 
         elem.pipe(
         //get the property and return the Observable

         )).asObservable(); 
}

So I basically need the equivalent of array[index] and object[key] and return Obeservable for BehaviorSubjects. How can I do that?

回答1:

you can use mergeMap to switch to that observable on the index, then you can use map to get the property value that you want I made example for you here: https://stackblitz.com/edit/angular-qzeuzt

来源：https://stackoverflow.com/questions/57754817/efficiently-get-observable-of-an-array-behaviorsubjects