assignable property
When you put a new object you don't assign an ID by default, it's assigned automatically by ObjectBox. If you need to assign IDs by yourself, use the @Id(assignable: true) annotation. This will allow putting an object with any valid ID. You can still set the ID to zero an leave it to ObjectBox. Note: in case you use assignable IDs on relation targets (with ToOne or ToMany), you're responsible for inserting new target objects before the source. If new objects have non-zero IDs ObjectBox has no way of telling which objects are new and which are already saved.
Implementation
final bool assignable;