rx

Observable.just(model)
    .flatMap {
        $0.rx.observe(String.self, "title")
    }
    .subscribe(onNext: { value in
        if let value = value {
            print("Title is \(value).")
        }
        }, onCompleted: {
            print("Completed")
        }, onDisposed: {
            print("Disposed")
    })
model
    .rx
    .deallocated
    .subscribe(onNext: {
        print("Model deallocated")
    })
model.title = "111"
model.title = "222"