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Tool for automated implementation of delegation pattern with ABC

Project description

abc-delegation

A tool for automated delegation with abstract base classes.

This metaclass enables creation of delegating classes inheriting from an abstract base class.

This technique is impossible with regular __getattr__ approach for delegation, so normally, you would have to define every delegated method explicitly. Not any more

Basic usage:

from abc import ABCMeta

from abc_delegation import delegation_metaclass

class A(metaclass=ABCMeta):
    @abstractmethod
    def bar(self):
        pass

    @abstractmethod
    def foo(self):
        pass

class B:
    def bar(self):
        return "B bar"

    def foo(self):
        return "B foo"

class C(A, metaclass=delegation_metaclass("my_delegate")):
    def __init__(self, b):
        self.my_delegate = b

    def foo(self):
        return "C foo"

c = C(B())
assert c.foo() == "C foo"
assert c.bar() == "B bar"

Multiple delegates:

from abc import ABCMeta

from abc_delegation import multi_delegation_metaclass


class A(metaclass=ABCMeta):
    @abstractmethod
    def bar(self):
        pass

    @abstractmethod
    def foo(self):
        pass

    @abstractmethod
    def baz(self):
        pass

class B:
    def bar(self):
        return "B bar"

    def foo(self):
        return "B foo"

class X:
    def baz(self):
        return "X baz"

class C(A, metaclass=multi_delegation_metaclass("_delegate1", "_delegate2")):
    def __init__(self, d1, d2):
        self._delegate1 = d1
        self._delegate2 = d2

    def foo(self):
        return "C foo"

c = C(B(), X())
assert c.bar() == "B bar"
assert c.foo() == "C foo"
assert c.baz() == "X baz"

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