adapter_concept.py

# pylint: disable=too-few-public-methods
# pylint: disable=arguments-differ
"Adapter Concept Sample Code"
from abc import ABCMeta, abstractmethod


class IA(metaclass=ABCMeta):
    "An interface for an object"
    @staticmethod
    @abstractmethod
    def method_a():
        "An abstract method A"


class ClassA(IA):
    "A Sample Class the implements IA"

    def method_a(self):
        print("method A")


class IB(metaclass=ABCMeta):
    "An interface for an object"
    @staticmethod
    @abstractmethod
    def method_b():
        "An abstract method B"


class ClassB(IB):
    "A Sample Class the implements IB"

    def method_b(self):
        print("method B")


class ClassBAdapter(IA):
    "ClassB does not have a method_a, so we can create an adapter"

    def __init__(self):
        self.class_b = ClassB()

    def method_a(self):
        "calls the class b method_b instead"
        self.class_b.method_b()


# The Client
# Before the adapter I need to test the objects class to know which
# method to call.
ITEMS = [ClassA(), ClassB()]
for item in ITEMS:
    if isinstance(item, ClassB):
        item.method_b()
    else:
        item.method_a()

# After creating an adapter for ClassB I can reuse the same method
# signature as ClassA (preferred)
ITEMS = [ClassA(), ClassBAdapter()]
for item in ITEMS:
    item.method_a()