@classmethod dan @staticmethod

Pendahuluan

Instance vs Kelas vs Statis

class Demo:
    def instance(self): return 'instance'
    @classmethod
    def class_m(cls): return f'class: {cls.__name__}'
    @staticmethod
    def static_m(): return 'static'
d = Demo()
print(d.instance())
print(Demo.class_m())
print(Demo.static_m())

@classmethod sebagai Pabrik

class Date:
    def __init__(self, y,m,d): self.y,self.m,self.d=y,m,d
    @classmethod
    def today(cls):
        from datetime import date
        d = date.today()
        return cls(d.year, d.month, d.day)
    def __repr__(self): return f'{self.y}-{self.m}-{self.d}'
print(Date.today())

@classmethod dengan Pewarisan

class Animal:
    @classmethod
    def create(cls, name):
        return cls(name)
    def __init__(self, name): self.name = name
class Dog(Animal): pass
d = Dog.create('Rex')
print(type(d).__name__, d.name)

@staticmethod untuk Utilitas

class MathHelper:
    @staticmethod
    def clamp(value, lo, hi):
        return max(lo, min(hi, value))
print(MathHelper.clamp(15, 0, 10))
print(MathHelper.clamp(-5, 0, 10))

@staticmethod vs Fungsi Modul

class Validator:
    @staticmethod
    def is_email(s): return '@' in s and '.' in s
print(Validator.is_email('user@example.com'))
print(Validator.is_email('not-an-email'))

Memanggil dari Instance

class C:
    @classmethod
    def who(cls): return cls.__name__
    @staticmethod
    def pi(): return 3.14
c = C()
print(c.who())
print(c.pi())

Metode Kelas untuk Singleton

class Singleton:
    _instance = None
    @classmethod
    def get(cls):
        if cls._instance is None:
            cls._instance = cls()
        return cls._instance
a = Singleton.get()
b = Singleton.get()
print(a is b)

Menimpa Classmethod

class Base:
    @classmethod
    def info(cls): return f'{cls.__name__} info'
class Child(Base): pass
print(Base.info())
print(Child.info())

Pemeriksaan Tipe dengan cls

class Shape:
    @classmethod
    def make(cls):
        return cls()  # NOT Shape()
class Square(Shape): pass
print(type(Square.make()).__name__)

Menggabungkan dengan @property

class Config:
    _data = None
    @classmethod
    def load(cls):
        if cls._data is None:
            cls._data = {'debug': True}
        return cls._data
print(Config.load())

Pemeriksaan Singkat

Ringkasan

Lanjutkan