Use cases

In this page, we will show the common use case of Autowire.

For instance, if want to run your application in multiple environment like development / production, You can change configuration by providing different values to each contexts.

Suppose that we have resources like that.

# in resources.py
import contextlib
from autowire import Resource, impl

from db_engine import DatabaseEngine

env = Resource('env', __name__)
db_config = Resource('db_config', __name__)
db_connection = Resource('db_connection', __name__)

@impl.plain(db_config, env)
def get_db_config(env):
    path = os.path.join('path/to/config', env, 'db.json')
    with open(path) as f:
        config = json.load(f)
    return config

@impl.contextual(db_connection, db_config)
@contextlib.contextmanager
def open_db_connection(db_config):
    conn = DatabaseEngine(db_config['HOST'], db_config['PORT'])
    try:
        yield conn
    finally:
        conn.close()

We can change running environment by providing env resource

# app.py
import os
from autowire import Context, impl

from .resources import env, db_connection

def run(db_connection):
    ...

app_context = Context()

@impl.plain(app_context(env))
def get_env():
    # Get env from envvar
    return os.environ['APP_ENV']

# APP_ENV will be injected to env resource.
with app_context.resolve(db_connection) as conn:
    run(conn)