Results<Element>.toObservable() -> Observable<Results<Element>>

Realm().doInTransaction<Element: Object>(
        object: [Element],
        inTransaction: @escaping ((Realm, [Element]) -> Void)) -> Completable

doInTransaction<Element: Object>(
        results: Results<Element>,
        inTransaction: @escaping ((Realm, Results<Element>) -> Void)) -> Completable

let realm = try! Realm()
realm.objects(Dog.self).toObservable().subscribe{
    // when Dog table changed, this print is called.
    print($0)
}

DispatchQueue.global(qos: .background).async {
    autoreleasepool {
        let realm = try! Realm()
        realm.objects(Dog.self).toObservable().subscribe {
            print($0)
        }
    }
}

let realm = try! Realm()
let dog = Dog()
dog.age = 1
dog.name = "pochi"

realm.doInTransaction(object: [dog]) { (realm: Realm, dogList: [Object]) in 
     realm.add(dogList.first!)
}.subscribe(onCompleted: {
    print("insert success.")
})

let provider = MoyaProvider<Dogs>()
provider
    .rx
    .request(.get)
    .observeOn(ConcurrentDispatchQueueScheduler(qos: .background))
    .map{
        let dog = Dog()
        dog.age = $0.age
        dog.name = $0.name
    }
    .flatMap {
        let realm = try! Realm()
        return realm.doInTransaction(object: [$0]) { realm, dogList in
            realm.add(dogList.first!)
        }
    }
    .subscribe {}