Pewarisan Ganda dan MRO

Pendahuluan

Sintaks Pewarisan Berganda

class A:
    def hello(self): return 'A'
class B:
    def world(self): return 'B'
class C(A, B): pass
c = C()
print(c.hello(), c.world())

Urutan Resolusi Metode (MRO)

class A:
    def greet(self): return 'A'
class B:
    def greet(self): return 'B'
class C(A, B): pass
print(C().greet())  # A wins
print(C.__mro__)

Linearisasi C3

class A: pass
class B(A): pass
class C(A): pass
class D(B, C): pass
print([c.__name__ for c in D.__mro__])

Pewarisan Berlian

class A:
    def __init__(self): print('A')
class B(A):
    def __init__(self): super().__init__(); print('B')
class C(A):
    def __init__(self): super().__init__(); print('C')
class D(B, C):
    def __init__(self): super().__init__(); print('D')
D()

Mixin

class JSONMixin:
    def to_json(self):
        import json
        return json.dumps(vars(self))
class User(JSONMixin):
    def __init__(self, name, age): self.name,self.age=name,age
print(User('Alice', 30).to_json())

Aturan Perancangan Mixin

class LoggingMixin:
    def log(self, msg): print(f'[{self.__class__.__name__}] {msg}')
class Service(LoggingMixin):
    def run(self): self.log('running')
Service().run()

super() dalam Pewarisan Berganda

class Base:
    def action(self): return 'Base'
class A(Base):
    def action(self): return 'A->' + super().action()
class B(Base):
    def action(self): return 'B->' + super().action()
class C(A, B):
    def action(self): return 'C->' + super().action()
print(C().action())

type() untuk Pembuatan Kelas Dinamis

def hello(self): return 'hello'
MyClass = type('MyClass', (object,), {'hello': hello})
print(MyClass().hello())

Memeriksa MRO

class A: pass
class B(A): pass
class C(B): pass
import inspect
print([c.__name__ for c in inspect.getmro(C)])

Kapan Menghindari Pewarisan Berganda

# Prefer:
class User:
    def __init__(self, name, logger):
        self.name = name
        self.logger = logger  # composition
print('composition preferred')

Pemeriksaan Singkat

Ringkasan

Lanjutkan