RXJS - dinstinctUntilChange with multiple keys

Issue

I want to fire .subscribe() for my oberservable if one of three object keys have changed.

it works, if I copy & paste the method for each key:

this.myService.loadData(this.dataContainer.id, true)
      .distinctUntilChanged((updatedData) => { return updatedData.relations; })
      .subscribe(updatedData => {
        console.log("relations changed",updatedData);
    });

this.myService.loadData(this.dataContainer.id, true)
      .distinctUntilChanged((updatedData) => { return updatedData.parent; })
      .subscribe(updatedData => {
        console.log("parent changed",updatedData);
    });

this.myService.loadData(this.dataContainer.id, true)
      .distinctUntilChanged((updatedData) => { return updatedData.children; })
      .subscribe(updatedData => {
        console.log("children changed",updatedData);
    });

if I set the distinctUntilChanged comparer to return the whole updatedData object, my subscribe never fires.

How can I combine the three dinstinctUntilChanged into one reducer?

Solution

One way:

const data$ = this.myService.loadData(this.dataContainer.id, true);

Observable
  .combineLatest(
    $data.distinctUntilChanged(data => updatedData.relations),
    $data.distinctUntilChanged(data => updatedData.parent),
    $data.distinctUntilChanged(data => updatedData.children),
    data => data
  )
  .subscribe(updatedData => {
    console.log("relation|parent|children changed", updatedData);
  });

Answered By - Lukas Neicelis