精通Python设计模式第二版 第 4 章 适配器模式 学习笔记
适配器模式
适配器模式是一种结构型设计模式，能帮助我们使两个不兼容的接口兼容。
假设我们想使用function_a()作为接口，但是只有function_b()，则可以使用适配器将function_b()转换(适配)为function_a()
实现
假设我们有这样一个需求：一个俱乐部活动，主要是通过聘请有才华的艺术家，组织演出和活动，来为客户提供娱乐活动
1. 定义Club类
organize_performance()方法是俱乐部可以执行的主要操作
class Club():
"""
Club :
Attributes:
"""
def __init__(self, name):
self.name = name
def __str__(self):
return f'the club {self.name}'
def organize_event(self):
return 'hires an artist to perform for the people'
2. 定义Musician类和Dance类
在Musician类中，主要动作有play()方法执行。在Dance类中，主要动作有dance()方法执行
class Musician():
"""
Musician :
Attributes:
"""
def __init__(self, name):
self.name = name
def __str__(self):
return f'the musician {self.name}'
def play(self):
return 'plays music'
class Dancer():
"""
Dancer :
Attributes:
"""
def __init__(self, name):
self.name = name
def __str__(self):
return f'the dancer {self.name}'
def dance(self):
return 'does a dance performance'
3. 定义适配器
它允许我们将具有不同接口的许多对象调整为一个统一的接口
adapted_method是一个字典，它包含与客户端调用的方法匹配的键值对
class Adapter():
"""
Adapter :
Attributes:
"""
def __init__(self, obj, adapted_methods):
self.obj = obj
self.__dict__.update(adapted_methods)
def __str__(self):
return str(self.obj)
4. 调用
当处理不同的类实例是，有如下两种情况
- 属于Club类的兼容对象不需要调整，我们可以直接使用它
- 首先需要使用Adapter类调整不兼容的对象
def main():
objects = [Club('Jazz Cafe'), Musician('Roy Ayers'), Dancer('Shane Sparks')]
for obj in objects:
if hasattr(obj, 'play') or hasattr(obj, 'dance'):
if hasattr(obj, 'play'):
adapted_methods = dict(organize_event=obj.play)
elif hasattr(obj, 'dance'):
adapted_methods = dict(organize_event=obj.dance)
# 此处指被适配的对象
obj = Adapter(obj, adapted_methods)
print(f'{obj} {obj.organize_event()}')
获得打印如下
the club Jazz Cafe hires an artist to perform for the people
the musician Roy Ayers plays music
the dancer Shane Sparks does a dance performance
完整代码如下
class Club():
"""
Club :
Attributes:
"""
def __init__(self, name):
self.name = name
def __str__(self):
return f'the club {self.name}'
def organize_event(self):
return 'hires an artist to perform for the people'
class Musician():
"""
Musician :
Attributes:
"""
def __init__(self, name):
self.name = name
def __str__(self):
return f'the musician {self.name}'
def play(self):
return 'plays music'
class Dancer():
"""
Dancer :
Attributes:
"""
def __init__(self, name):
self.name = name
def __str__(self):
return f'the dancer {self.name}'
def dance(self):
return 'does a dance performance'
class Adapter():
"""
Adapter :
Attributes:
"""
def __init__(self, obj, adapted_methods):
self.obj = obj
self.__dict__.update(adapted_methods)
def __str__(self):
return str(self.obj)
def main():
objects = [Club('Jazz Cafe'), Musician('Roy Ayers'), Dancer('Shane Sparks')]
for obj in objects:
if hasattr(obj, 'play') or hasattr(obj, 'dance'):
if hasattr(obj, 'play'):
adapted_methods = dict(organize_event=obj.play)
elif hasattr(obj, 'dance'):
adapted_methods = dict(organize_event=obj.dance)
# 此处指被适配的对象
obj = Adapter(obj, adapted_methods)
print(f'{obj} {obj.organize_event()}')
if __name__ == '__main__':
main()
