A kotlin extension to allow shared preference values to be observed

SharedPreferencesObservable.kt

inline fun <reified T> SharedPreferences.observe(keyToObserve: String, defaultValue: T): Observable<T> {
    return Observable.create<T> { emitter ->
        val listener = SharedPreferences.OnSharedPreferenceChangeListener { sharedPreferences, key ->
            if (key == keyToObserve) {

                val value = sharedPreferences.all[key]
                if (value is T) {
                    emitter.onNext(value)
                } else {
                    Timber.w("SharedPreferences", "Warning: observed preference type does not match")
                }
            }
        }

        emitter.setCancellable { unregisterOnSharedPreferenceChangeListener(listener) }
        registerOnSharedPreferenceChangeListener(listener)

        //emit initial value
        val initialValue: T = all[keyToObserve]?.run {
            if (this is T) {
                this
            } else {
                defaultValue
            }
        } ?: defaultValue

        emitter.onNext(initialValue)

    }
            .replay(1)
            .refCount()
}