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monostate.py
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112 lines (85 loc) · 3.16 KB
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# coding: utf-8
__doc__ = '''
简单设计模式（monostate）意图：
1、确保有且只有一个对象被创建
2、为对象提供一个访问点，以程序可以全局访问该对象
3、控制共享资源的并行访问
'''
class Singleton(object):
__doc__ = "只会生成一个实例"
def __new__(cls, *args, **kwargs):
# 使用hasattr方法检查cls是否存在instance实例，如果存在直接返回instance，如果不存在则生成一个
if not hasattr(cls, 'instance'):
cls.instance = super(Singleton, cls).__new__(cls)
return cls.instance
class SingletonA(object):
__doc__ = "懒汉实例化，只有在使用对象时才实例化对象，节约资源"
__instance = None
def __init__(self):
if not SingletonA.__instance:
print "__init__ method called.."
else:
print "Instance already created:", self.get_instance()
@classmethod
def get_instance(cls):
if not cls.__instance:
cls.__instance = SingletonA()
return cls.__instance
class Borg:
__doc__ = '''共享模式，类可以生成多个实例，但是这些实例数据相同，
任何一个实例数据改变会引起其他实例的数据改变'''
__shared_state = {"l": 3, "1": 2}
# 为什么在这里添加y成员是正常的在init中添加y成员报错？
# y = 2
def __init__(self):
self.x = 1
self.y = 2
# __dict__是类保存成员的，当定义x的时候，x被加到__dict__中，但是为什么y没有被加到__dict__中呢？
# 当赋值后__dict__中的key就是类的成员
self.__dict__ = self.__shared_state
pass
# python 3.5有效
class MyInt(type):
__doc__ = "从元类派生的新类，即定义了一个数据类型，type(实例)结果为MyInt"
def __call__(cls, *args, **kwargs):
print "******Here`s My Int********"
print "Now do whatever you want wish these object..."
return type.__call__(cls, *args, **kwds)
class int:
__metaclass__ = MyInt
def __init__(self, x, y):
self.x = x
self.y = y
if __name__ == "__main__":
__doc__ = "self test"
print __doc__
print "---------------单例模式-----------------"
s = Singleton()
print "Object create ", s
s1 = Singleton()
print "Object create ", s1
print "---------------------------------------"
print "\n"
print "----------------懒汉实例化---------------"
s2 = SingletonA()
print "Object create", SingletonA.get_instance()
s3 = SingletonA()
print "----------------------------------------"
print "\n"
print "--------------共享状态-------------------"
a = Borg()
a1 = Borg()
print a.l
print a1.l
print "Borg object 'a':", a
print "Borg object 'a1':", a1
a1.x = 4
print "Object state 'a':", a.__dict__
print "Object state 'a1'", a1.__dict__
# print "Object value x, y 'a':", a.x, a.y
# print "Object Value x, y 'a1':", a1.x, a1.y
print "-----------------------------------------"
print "\n"
print "---------------元类-----------------------"
b = int(6, 7)
print b