RxSwift Realm observe Array in RunLoop - ios

Question

I am using RxSwift and RxRealm and want to be able to observe changes of resources based on a predicate. The function would be like this
func observe(type: String) -> Observable<[MyRealmObject]> {
let realm = configureRealm() // 1
let predicate = NSPredicate(format: "type = %#", type)
let resources = realm
.objects(MyRealmObject.self)
.filter(predicate)
return Observable.array(from: resources) // 2
}
However, Realm requires // 2 to be run on a thread with a run loop AND // 1 and // 2 have to be called on the same thread.
I can't guarantee that the observe(type: String) function is already being called on a thread with run loop, so I probably have to switch to one within the function - but that way i wont be able to have a synchronous return value anymore.
Any ideas on how to make sure realm observations are always guaranteed to be on a specific run loop?
Update: Using custom Thread with run-loop - but I'm still not satisfied
I created a custom thread that has a run loop but getting the synchronous return value is just ugly - as you can see i used a DispatchGroup to synchronize and i'd really like to avoid that.
func observe(type: String) -> Observable<[MyRealmObject]> {
let observableCalculation = {
let realm = configureRealm() // 1
let predicate = NSPredicate(format: "type = %#", type)
let resources = realm
.objects(MyRealmObject.self)
.filter(predicate)
return Observable.array(from: resources) // 2
}
if Thread.current == self.realmObservationThread {
return observableCalculation()
}
var o: Observable<[MyRealmObject]>!
let g = DispatchGroup()
g.enter()
self.realmObservationThread.runloop?.perform {
o = observableCalculation()
g.leave()
}
g.wait()
return o
}
Any suggestions would be appreciated!

Answer 1

Do you really have to observe each and every array individually by creating the observable. I think it is better to observe Results which is the result of query instead of Observing each items like so.
See sample from here.
You could then wrap this inside your own observable and based on the changes in the Result, you could then do a callback for specific object.