Registry

The injectme.DependenciesRegistry is on of the two core classes used by injectme. Registry’s responsiblity is to store instances and factories for registered dependencies.

The injectme.register(), injectme.register_factory() and injectme.clear_dependencies() are all shortcuts for calling appropriate methods on a single global DependenciesRegistry instance created by injectme to provide Simple API.

You can create your own instance of DependenciesRegistry. It’s not very usefule on it’s own but provides foundation of dependencies management for injectme.Injector.

Example:

example.py

from injectme import (
    DependenciesRegistry,
    DependencyNotFound,
    DependencyAlreadyRegistered,
)

class DependencyA:
    pass


class DependencyB:
    pass


registry = DependenciesRegistry()

# there's no dependencies registered so we'll get an
# exception trying to get one
try:
    registry.get(DependencyA)
except DependencyNotFound as err:
    print("Dependency not found:")
    print(err)


# let's register an instance
dep_a = DependencyA()
registry.register_instance(DependencyA, dep_a)

# and with 'get()' call we can get same instance from the registry
print("Getting DependencyA")
registered_dep_a = registry.get(DependencyA)
print("Got same instance?", dep_a is registered_dep_a)


# let's register a factory
def dep_b_factory():
    print("Creating DependencyB")
    return DependencyB()

registry.register_factory(DependencyB, dep_b_factory)

# same as before, use 'get()' to get instance of registered dependency
print("Getting DependencyB")
dep_b_1 = registry.get(DependencyB)
dep_b_2 = registry.get(DependencyB)

# the factory is being called for each 'get()'
print("Got same instance?", dep_b_1 is dep_b_2)


# trying to register same dependency twice
try:
    registry.register_instance(DependencyA, DependencyA())
except DependencyAlreadyRegistered as err:
    print("Dependency already registered:")
    print(err)


# clearing registry
print("Clear registry")
registry.clear()

try:
    registry.get(DependencyA)
except DependencyNotFound as err:
    print("Dependency not found:")
    print(err)

$ python3 example.py

Dependency not found:
Dependency <class '__main__.DependencyA'> has not been found in the registry

Getting DependencyA
Got same instance? True

Getting DependencyB
Creating DependencyB
Creating DependencyB
Got same instance? False

Dependency already registered:
Dependency <class '__main__.DependencyA'> already registered

Clear registry
Dependency not found:
Dependency <class '__main__.DependencyA'> has not been found in the registry