问题
I'm trying to convert documents to objects from Firestore, but when I create my data class , I dont know how to initialize the GeoPoint with default values as it needs to be declared for an empty constructor
data class MapObj(val geopoint:Geopoint) //--> how to initialize it to get an empty constructor
The problem relies on this line
val obj = snapshot.toObject(MapObj::class.java)
Thanks
回答1:
The problem is that the Firestore SDK isn't finding a default, no argument constructor for MapObj. Kotlin data classes don't have one if all of their properties are declared with val. For properties declared val, Kotlin requires that their values be specified in the constructor, since they can't possibly change afterward.
If you must get a data class back from Firestore, you will have to make all of its properties optional var with a default value, so that Kotlin will generate a no-arg constructor for it.
data class MapObj(var geopoint: Geopoint? = null)
来源：https://stackoverflow.com/questions/57563216/how-to-initialize-default-values-for-geopoint-in-a-data-class