Foreign keys support

The database models support foreign keys. Example: create a foreign key model:

class Manufacturer with DbModel {
    Manufacturer({this.name});

    final String name;

    @override
    int id;

    @override
    Db get db => conf.db;

    @override
    DbTable get table => manufacturerTable;

    @override
    Map<String, dynamic> toDb() => <String, dynamic>{"name": name};

    @override
    Manufacturer fromDb(Map<String, dynamic> map) =>
        Manufacturer(name: map["name"].toString());
}

To set a foreign key mention it in your table schema:

final carTable = DbTable("car")
   ..varchar("name")
   ..real("price")
   ..foreign_key("manufacturer");

Update the serializers in the main model to use the foreign key:

class Car with DbModel {
    @override
    Map<String, dynamic> toDb() {
        final row = <String, dynamic>{
            // ...
            "manufacturer": manufacturer.id
        };
    return row;
    }

    @override
    Car fromDb(Map<String, dynamic> map) {
        final car = Car(
            // ...
        );
        // the key will be present only with join queries
        // in a simple select this data is not present
        if (map.containsKey("manufacturer")) {
            car.manufacturer =
                Manufacturer().fromDb(map["manufacturer"] as Map<String, dynamic>);
        }
        return car;
    }
}

To perform a join query:

class Car with DbModel {
    static Future<List<Car>> selectRelated({String where, int limit}) async {
        final cars = List<Car>.from(
            await Car().sqlJoin(where: where, limit: limit));
        return cars;
    }
}

And then use it:

List<Car> cars = await Car.selectRelated(where: "price<50000");
print(cars[0].manufacturer.name);