组合与封装

Posted 2021-01-28 huangchaonan

1. 什么是组合
组合指的是某一个对象拥有一个属性,该属性的值是另外一个类的对象
class Foo:
pass

class Bar:
pass

obj=Foo()
obj.attr=Bar()

obj.xxx
obj.attr.yyy

2. 为何要用组合
通过为某一个对象添加属性(属性的值是另外一个类的对象)的方式,可以间接地将两个类关联/整合/组合到一起
从而减少类与类之间代码冗余

class Foo1:
pass
class Foo2:
pass
class Foo3:
pass

class Bar:
pass

obj_from_bar=Bar()

obj1=Foo1()
obj2=Foo2()
obj3=Foo3()

obj1.attr1=obj_from_bar
obj2.attr2=obj_from_bar
obj3.attr3=obj_from_bar
obj2.attr2=obj_from_bar
obj1.attr1=

3. 如何用组合

class OldboyPeople:
school = ‘Oldboy‘

def __init__(self,name,age,sex,):
self.name = name
self.age = age
self.sex = sex

class OldboyStudent(OldboyPeople):
def __init__(self, name, age, sex,score=0):
OldboyPeople.__init__(self,name,age,sex)
self.score = score

def choose_course(self):
print(‘%s choosing course‘ % self.name)

class OldboyTeacher(OldboyPeople):
def __init__(self,name,age,sex,level):
OldboyPeople.__init__(self,name,age,sex)
self.level=level

def score(self,stu,num):
stu.score=num

class Course:
def __init__(self,c_name,c_price,c_period):
self.c_name = c_name
self.c_price = c_price
self.c_period = c_period

def tell_info(self):
print(‘<课程名:%s 价钱:%s 周期:%s>‘ %(self.c_name,self.c_price,self.c_period))

# 创建课程对象
python=Course(‘python全栈开发‘,1900,‘5mons‘)
linux=Course(‘linux架构师‘,900,‘3mons‘)

stu1=OldboyStudent(‘刘二蛋‘,38,‘male‘)
stu1.course=python
# print(stu1.__dict__)

stu1.course.tell_info()

tea1=OldboyTeacher(‘egon‘,18,‘male‘,10)
tea1.course=python
# print(tea1.__dict__)
tea1.course.tell_info()

 

class OldboyPeople:
school = ‘Oldboy‘

def __init__(self,name,age,sex,):
self.name = name
self.age = age
self.sex = sex

class OldboyStudent(OldboyPeople):
def __init__(self, name, age, sex,score=0):
OldboyPeople.__init__(self,name,age,sex)
self.score = score
self.courses=[]

def choose_course(self):
print(‘%s choosing course‘ % self.name)

def tell_all_course(self):
print((‘学生[%s]选修的课程如下‘ %self.name).center(50,‘=‘))
for obj in self.courses:
obj.tell_info()
print(‘=‘*60)

class OldboyTeacher(OldboyPeople):
def __init__(self,name,age,sex,level):
OldboyPeople.__init__(self,name,age,sex)
self.level=level
self.courses=[]

def score(self,stu,num):
stu.score=num

def tell_all_course(self):
print((‘老师[%s]教授的课程如下‘ %self.name).center(50,‘*‘))
for obj in self.courses:
obj.tell_info()
print(‘*‘*70)

class Course:
def __init__(self,c_name,c_price,c_period):
self.c_name = c_name
self.c_price = c_price
self.c_period = c_period

def tell_info(self):
print(‘<课程名:%s 价钱:%s 周期:%s>‘ %(self.c_name,self.c_price,self.c_period))

# 创建课程对象
python=Course(‘python全栈开发‘,1900,‘5mons‘)
linux=Course(‘linux架构师‘,900,‘3mons‘)

stu1=OldboyStudent(‘刘二蛋‘,38,‘male‘)
stu1.courses.append(python)
stu1.courses.append(linux)
# print(stu1.courses)
stu1.tell_all_course()

tea1=OldboyTeacher(‘egon‘,18,‘male‘,10)
tea1.courses.append(python)
# print(tea1.courses)
tea1.tell_all_course()

 

 

‘‘‘
1. 什么是封装
装:往容器/名称空间里存入名字
封:代表将存放于名称空间中的名字给藏起来,这种隐藏对外不对内

2. 为何要封装
封数据属性:??? 将数据属性隐藏起来,类外就无法直接操作属性,需要类内开辟一个接口来外部的使用可以间接地操作属性,可以在接口内定义任意的控制逻辑,从而严格控制使用对属性的操作
封函数属性:??? 隔离复杂度

3. 如何封装
在类内定义的属性前加__开头(没有__结果)
总结:
1. __开头的属性实现的隐藏仅仅只是一种语法意义上的变形,并不会真的限制类外部的访问
2. 该变形操作只在类定义阶段检测语法时发生一次,类定义阶段之后新增的__开头的属性并不会变形
3. 如果父类不想让子类覆盖自己的属性,可以在属性前加__开头
‘‘‘
class Foo:
__x=111 # _Foo__x
__y=222 # _Foo__y

def __init__(self,name,age):
self.__name=name
self.__age=age

def __func(self): #_Foo__func
print(‘func‘)

def get_info(self):
print(self.__name,self.__age,self.__x) #print(self._Foo__name,self._Foo__age,self._Foo__x)

# print(Foo.__x)
# print(Foo.__func)
# print(Foo.__dict__)
# print(Foo._Foo__x)
# print(Foo._Foo__y)
# Foo.__z=333
# print(Foo.__dict__)
# print(Foo.__z)

obj=Foo(‘egon‘,18)
# print(obj.__dict__)
# print(obj.__name)
# print(obj.__age)
# obj.get_info()

obj.__sex=‘male‘
# print(obj.__dict__)
# print(obj.__sex)

# obj.get_info()
# 1. __开头的属性到底如何实现的隐藏?
# 2. 如何实现的对外隐藏,对内不隐藏

 

class Foo:
def __f1(self): #_Foo__f1
print(‘Foo.f1‘)

def f2(self):
print(‘Foo.f2‘)
self.__f1() #obj._Foo__f1()

class Bar(Foo):
def __f1(self): # _Bar__f1
print(‘Bar.f1‘)

obj=Bar()

# obj.f2()
‘‘‘
Foo.f2
Bar.f1
‘‘‘

# 封装数据属性:将数据属性隐藏起来,类外就无法直接操作属性,需要类内开辟一个接口来外部的使用可以间接地操作属性,可以在接口内定义任意的控制逻辑,
# 从而严格控制使用对属性的操作

class People:
def __init__(self,name,age):
self.__name=name
self.__age=age

def tell_info(self):
print(‘<name:%s age:%s>‘ %(self.__name,self.__age))

def set_info(self,name,age):
if type(name) is not str:
print(‘名字必须是str类型傻叉‘)
return
if type(age) is not int:
print(‘年龄必须是int类型傻叉‘)
return
self.__name=name
self.__age=age

obj=People(‘egon‘,18)
# obj.tell_info()

# obj.set_info(‘EGON‘,19)
# obj.set_info(123,19)
obj.set_info(‘EGON‘,‘18‘)
obj.tell_info()

 

# 封装函数属性:隔离复杂度
class ATM:
def __card(self):
print(‘插卡‘)
def __auth(self):
print(‘用户认证‘)
def __input(self):
print(‘输入取款金额‘)
def __print_bill(self):
print(‘打印账单‘)
def __take_money(self):
print(‘取款‘)

def withdraw(self):
self.__card()
self.__auth()
self.__input()
self.__print_bill()
self.__take_money()

a=ATM()
a.withdraw()