Structured Configs example

This example demonstrates the use of Structured Configs to instantiated objects.

Example usage

my_app.py

class DBConnection:
    def __init__(self, driver: str, host: str, port: int) -> None:
        self.driver = driver
        self.host = host
        self.port = port

    def connect(self) -> None:
        print(f"{self.driver} connecting to {self.host}")

class MySQLConnection(DBConnection):
    def __init__(self, driver: str, host: str, port: int) -> None:
        super().__init__(driver=driver, host=host, port=port)

class PostgreSQLConnection(DBConnection):
    def __init__(self, driver: str, host: str, port: int, timeout: int) -> None:
        super().__init__(driver=driver, host=host, port=port)
        self.timeout = timeout

@dataclass
class DBConfig:
    driver: str = MISSING
    host: str = "localhost"
    port: int = 80

@dataclass
class MySQLConfig(DBConfig):
    _target_: str = "my_app.MySQLConnection"
    driver: str = "MySQL"
    port: int = 1234

@dataclass
class PostGreSQLConfig(DBConfig):
    _target_: str = "my_app.PostgreSQLConnection"
    driver: str = "PostgreSQL"
    port: int = 5678
    timeout: int = 10

@dataclass
class Config:
    defaults: List[Any] = field(default_factory=lambda: [{"db": "mysql"}])
    db: DBConfig = MISSING


cs = ConfigStore.instance()
cs.store(name="config", node=Config)
cs.store(group="db", name="mysql", node=MySQLConfig)
cs.store(group="db", name="postgresql", node=PostGreSQLConfig)

@hydra.main(config_name="config")
def my_app(cfg: Config) -> None:
    connection = instantiate(cfg.db)
    connection.connect()

if __name__ == "__main__":
    my_app()

Sample Output

$ python my_app.py
MySQL connecting to localhost:1234

$ python my_app.py db=postgresql
PostgreSQL connecting to localhost:5678