Vaccine
Vaccine is a tiny dependency injection framework for Python.
Usage
At Vaccine's core is an instance of vaccine.Vaccine. Think of Vaccine as a
dict that automatically builds things for you as necessary. Begin by instantiating a single, global instance of Vaccine
i = Vaccine()Next, register classes and functions as requiring and providing dependencies
with Vaccine.requires and Vaccine.provides (make sure provides appears
before requires!).
class SomeServiceInterface(object):
pass
# register this class as providing for some interface and requiring some
# dependencies (this time, keyed on strings)
@i.provides(SomeServiceInterface) # you can uses interfaces as keys...
@i.requires(host="HOST", credentials="CREDENTIALS") # or just strings
class SomeService(SomeServiceInterface):
def __init__(self, host, credentials):
print '<SomeService>'
self.host = host
self.credentials = credentials
def hello_world(self):
print "Logging into: {}".format(self.host)
print "Username: {}".format(self.credentials['user'])
print "Password: {}".format(self.credentials['password'])
# In addition to classes, you can also annotate functions with `provides` and
# `requires`.
@i.provides("CREDENTIALS")
def credentials():
print '<credentials>'
import os
return {"user": os.environ["USER"], "password": "XXXX"}
# rather than registering a providing function/class that provide for a key,
# you can register already-instantiated values directly.
i.register("HOST", "localhost")Finally, use Vaccine.get(key) to retrieve already-built dependencies. Each
key will only be called once.
# manually retrieving an instantiation is as sample as calling `get`. All
# dependencies will be handled automatically.
service = i.get(SomeServiceInterface)
service.hello_world()
# keys are only instantiated once
service2 = i.get(SomeServiceInterface)
service is service2 # True
