Extension to avoid false positive in room query

LiveDataExtensions.kt

/*
Extension to avoid false positive in room query :
https://stackoverflow.com/questions/47215666/room-livedata-from-dao-will-trigger-observer-onchanged-on-every-update-even-i
https://medium.com/androiddevelopers/7-pro-tips-for-room-fbadea4bfbd1#5e38
*/
fun <T> LiveData<T>.getDistinct(): LiveData<T> {
    val distinctLiveData = MediatorLiveData<T>()
    distinctLiveData.addSource(this, object : Observer<T> {
        private var initialized = false
        private var lastObj: T? = null
        override fun onChanged(obj: T?) {
            if (!initialized) {
                initialized = true
                lastObj = obj
                distinctLiveData.postValue(lastObj)
            } else if ((obj == null && lastObj != null)
                || obj != lastObj) {
                lastObj = obj
                distinctLiveData.postValue(lastObj)
            }
        }
    })
    return distinctLiveData
}