Examples

Type resolution by type hints inside constructors

Consider the example below:

from abc import ABC, abstractmethod

# domain object:
class Cat:

    def __init__(self, name):
        self.name = name

# abstract interface
class ICatsRepository(ABC):

    @abstractmethod
    def get_by_id(self, _id) -> Cat:
        pass


# one of the possible implementations of ICatsRepository
class InMemoryCatsRepository(ICatsRepository):

    def __init__(self):
        self._cats = {}

    def get_by_id(self, _id) -> Cat:
        return self._cats.get(_id)


# NB: example of business layer class, using interface of repository
class GetCatRequestHandler:

    def __init__(self, cats_repository: ICatsRepository):
        self.repo = cats_repository

---

rodi configuration to obtain instances of GetCatRequestHandler would look like this:

# (imports omitted...)
from rodi import ServiceCollection

services = ServiceCollection()

# configuring services...
services.add_transient(ICatsRepository, InMemoryCatsRepository)
services.add_exact_transient(GetCatRequestHandler)

# building the provider
provider = services.build_provider()

# obtaining instances of services:
get_cat_handler = provider.get(GetCatRequestHandler)

assert isinstance(get_cat_handler, GetCatRequestHandler)
assert isinstance(get_cat_handler.repo, InMemoryCatsRepository)

Type resolution by parameter names

In this example, type resolution happens by parameter name, when requiring Foo service, a new one is instantiated passing the configured singleton of Settings to its constructor.

class Foo:

    def __init__(self, settings):
        self.settings = settings


class Settings:
    def __init__(self, db_connection_string):
        self.db_connection_string = db_connection_string


# in some other module..
from rodi import ServiceCollection

services = ServiceCollection()

# configuring services...
services.add_instance(Settings("whatever/connection/string"))
services.add_exact_transient(Foo)

# building the provider
provider = services.build_provider()

# obtaining instances of services:
foo = provider.get(Foo)

assert isinstance(foo, Foo)
assert isinstance(foo.settings, Settings)

More examples in tests code

Please look at tests code, for more examples.