Dart APIunself_local_databaseFieldextra extra property Null safety TextColumn extra Implementation TextColumn get extra => text()(); unself_local_database unself_local_database Field extra property Field class Constructors Field Properties collectionId created customConstraints dontWriteConstraints extra hashCode id isStrict name primaryKey required runtimeType system tableName type unique uniqueKeys updated withoutRowId Methods blob boolean dateTime int64 integer intEnum noSuchMethod real text textEnum toString Operators operator ==