Provide convenience extension function

realtimedb/src/main/kotlin/de/sipgate/federmappe/realtimedb/DatabaseReferenceExt.kt

@@ -0,0 +1,46 @@
+package de.sipgate.federmappe.realtimedb
+
+import com.google.firebase.database.DataSnapshot
+import com.google.firebase.database.DatabaseError
+import com.google.firebase.database.DatabaseReference
+import com.google.firebase.database.ValueEventListener
+import kotlinx.coroutines.channels.awaitClose
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.callbackFlow
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.SerializationException
+import kotlinx.serialization.serializer
+
+
+@ExperimentalSerializationApi
+inline fun <reified T: Any> DatabaseReference.toObject(
+    serializer: KSerializer<T> = serializer<T>(),
+    crossinline errorHandler: (Throwable) -> T? = { throw it }
+): Flow<T> {
+    return callbackFlow {
+        val valueEventListener = object : ValueEventListener {
+            override fun onCancelled(error: DatabaseError) {
+                close(IllegalStateException(error.toException()))
+            }
+
+            override fun onDataChange(dataSnapshot: DataSnapshot) {
+                val decodedAppData =
+                    try {
+                        dataSnapshot.toObjectWithSerializer(serializer)
+                    } catch (ex: SerializationException) {
+                        errorHandler(ex)
+                    }
+
+                if (decodedAppData != null) {
+                    trySend(decodedAppData)
+                }
+            }
+        }
+
+        this@toObject.addValueEventListener(valueEventListener)
+
+        awaitClose { this@toObject.removeEventListener(valueEventListener) }
+    }
+}
+