Dart APIunself_local_databaseCollectionCompanionviewRule viewRule property Null safety Value<String?> viewRule final Implementation final Value<String?> viewRule; unself_local_database unself_local_database CollectionCompanion viewRule property CollectionCompanion class Constructors CollectionCompanion insert Properties created createRule deleteRule extra hashCode id listRule name runtimeType system type updated updateRule viewRule Methods copyWith noSuchMethod toColumns toString Operators operator == Static methods custom