Nice Kotlin Extensions for Google Firestore

FirestoreExtensions.kt

fun test() {

    class City(var name: String, var location: GeoPoint)

    var query = FirebaseFirestore.getInstance().collection("city").limit(10)
    var error : (Exception) -> Unit = { it.printStackTrace() }

    query.query<City>(callbackWithKey = { keyList, cityList -> }, error = error)
    query.query(callback = { documentSnapshotList -> }, error = error)
    query.addChangeListener(isAdded = {}, isRemoved = {}, isModified = {}, error = error)

}

infix fun <T : Any> DocumentSnapshot.convertAs(classType: Class<T>) = toObject(classType)

inline fun <reified T : Any> Query.query(crossinline callbackWithKey: (List<String>, List<T>) -> Unit, crossinline error: (Exception) -> Unit = { it.printStackTrace() }) {
    get().addOnSuccessListener {
        callbackWithKey(it.documents.map { it.id }, it.documents.map { it convertAs T::class.java })
    }.addOnFailureListener {
        error(it)
    }
}

inline fun Query.query(crossinline callback: (List<DocumentSnapshot>) -> Unit, crossinline error: (Exception) -> Unit = { it.printStackTrace() }) {
    get().addOnSuccessListener {
        callback(it.documents)
    }.addOnFailureListener {
        error(it)
    }
}

inline fun Query.addChangeListener(
        crossinline isAdded: (DocumentSnapshot) -> Unit,
        crossinline isRemoved: (DocumentSnapshot) -> Unit,
        crossinline isModified: (DocumentSnapshot) -> Unit,
        crossinline error: (Exception) -> Unit = { it.printStackTrace() }) {
    addSnapshotListener { querySnapshot, fe ->
        if (fe != null || querySnapshot == null) {
            error(fe)
            return@addSnapshotListener
        }
        querySnapshot.documentChanges.forEach {
            when (it.type) {
                DocumentChange.Type.ADDED -> isAdded(it.document)
                DocumentChange.Type.REMOVED -> isRemoved(it.document)
                DocumentChange.Type.MODIFIED -> isModified(it.document)
            }
        }
    }
}