hexdi 0.2.2

Highly extensible Dependency injection framework for humans

hexdi

Highly extensible Dependency Injection framework for humans

Project location: https://github.com/zibertscrem/hexdi

Installation

pip install hexdi

You should have python 3.5.* or higher

Usage

All of that usages you can find in examples directory

Quick usage reference

import hexdi


class SomeA:
    def foo(self): pass


# mark that class as injectable with permanent lifetime for class SomeA
@hexdi.permanent(SomeA)
class SomeAimplementation(SomeA):
    def foo(self):
        return 42


# inject instance of SomeA as a first argument
@hexdi.inject(SomeA)
def test_injection(a: SomeA):
    print('test_injection:', a.foo())


class ClassWithDependency:
    # constructor injection
    @hexdi.inject(SomeA)
    def __init__(self, a: SomeA):
        print('ClassWithDependency.__init__:', a.foo())

    # after that we can use property like an instance of SomeA class
    @property
    @hexdi.dependency(SomeA)
    def some_a(self) -> SomeA: pass

    def foo(self):
        print('ClassWithDependency.foo:', self.some_a.foo())

    # method injection also works fine.
    # Because injection members are passing after all transmitted positional arguments
    @hexdi.inject(SomeA)
    def foo_with_injection(self, a: SomeA):
        print('ClassWithDependency.foo_with_injection:', a.foo())


if __name__ == '__main__':
    # You don't need to provide any argument. DI container does it self
    # There also should not be cycle dependencies due to lazy loading of any injections
    test_injection()  # prints: test_injection: 42
    cwd = ClassWithDependency()  # prints: ClassWithDependency.__init__: 42
    cwd.foo()  # prints: ClassWithDependency.foo: 42
    cwd.foo_with_injection()  # prints: ClassWithDependency.foo_with_injection: 42

Self-binding

import hexdi


@hexdi.permanent()
class SomeA:
    def foo(self):
        return 42


@hexdi.inject(SomeA)
def test(a):
    print(a.foo())


if __name__ == '__main__':
    test()  # prints: 42

Multiple injection arguments

import hexdi


@hexdi.permanent()
class SomeA:
    def foo(self):
        return 42


@hexdi.permanent()
class SomeB:
    def foo(self):
        return 69


@hexdi.inject(SomeA, SomeB)
def test(a, b):
    print(a.foo() + b.foo())


if __name__ == '__main__':
    test()  # prints: 111

Permanent lifetime and transient lifetime

import hexdi


@hexdi.permanent()
class SomeA:
    NUMBER = 0

    def __init__(self):
        self.num = SomeA.NUMBER
        SomeA.NUMBER += 1

    def foo(self):
        print(self.__class__.__name__, self.num)


@hexdi.transient()
class SomeB:
    NUMBER = 0

    def __init__(self):
        self.num = SomeB.NUMBER
        SomeB.NUMBER += 1

    def foo(self):
        print(self.__class__.__name__, self.num)


@hexdi.inject(SomeA)
def test_a(a):
    a.foo()


@hexdi.inject(SomeB)
def test_b(b):
    b.foo()


if __name__ == '__main__':
    test_a()  # prints: SomeA 0
    test_a()  # prints: SomeA 0
    test_a()  # prints: SomeA 0
    test_b()  # prints: SomeB 0
    test_b()  # prints: SomeB 1
    test_b()  # prints: SomeB 2

Usage of container. Demonstration of lazy injection

import hexdi


class SomeA:
    def foo(self): pass


class SomeAImplementation(SomeA):
    def foo(self):
        return 42


@hexdi.permanent()
class SomeB:
    def foo(self):
        return 69


class SomeC:
    def foo(self):
        return 100500


@hexdi.inject(SomeC)
def test(c):
    print(c.foo())


if __name__ == '__main__':
    # getting of container
    container = hexdi.get_root_container()
    # binding SomeAImplementation on SomeA type with permanent lifetime
    container.bind_type(SomeAImplementation, SomeA, hexdi.lifetime.PermanentLifeTimeManager)
    instance = container.resolve(SomeA)
    print(instance.foo())  # prints: 42
    # resolve decorator-binded SomeB
    instance = container.resolve(SomeB)
    print(instance.foo())  # prints: 69
    # bind SomeC on itself with permanent lifetime
    container.bind_type(SomeC, SomeC, hexdi.lifetime.PermanentLifeTimeManager)
    # we mark SomeC for injection above in test func,
    # but all works fine, because it is lazy injection
    test()  # prints: 100500

Multifile project

If you have a project with separated base objects(to registration) and implementations(to injecting) there will be problematically to identify these implementations if you import it nowhere. For that situation, there is a class loading abstraction with a basic implementation that gets a list of specification objects with implementation modules. These specification object can be: - dot-separated module path as string: ‘pack1.pack2.module1’ - a function/lambda without params that returns a specification - a tuple that contains a function as a first argument and tuple of values as a second argument. Function should return a specification

import hexdi
from examples.multifile.interfaces import SomeA

loader = hexdi.get_loader([
    'examples.multifile.implementations'
])


@hexdi.inject(SomeA)
def test(a: SomeA):
    print(a.foo())


if __name__ == '__main__':
    loader.load()
    test()  # prints: 42

You also able to use recursive module finder to find all local packages, site-packages, dist-packages modules that contains type registering. Use same rules as module loader has

import hexdi
from examples.multifile.interfaces import SomeA

# That finder will find that
finder = hexdi.get_finder(['examples.multifile-finder'])
loader = hexdi.get_loader(finder.find())


@hexdi.inject(SomeA)
def test(a: SomeA):
    print(a.foo())


if __name__ == '__main__':
    loader.load()
    test()  # prints: 69