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• Catalog
• Appearance mode （Facade）
• Application scenarios
• Code example

Appearance mode （Facade）

Appearance mode （Facade）, Provides a consistent interface for a set of interfaces in a subsystem . The facade pattern defines a high-level interface , This interface makes this subsystem easier to use .

The difference between appearance mode and adapter mode is ： Appearance mode is to design a unified interface for small systems under large systems , The adapter mode is designed for various interface calls of different systems .

advantage ：

1. Subsystem and Client The loose coupling relationship between .
2. Client Shielding subsystem components , Less Client Number of objects to process , And make it easier to use the subsystem .

Application scenarios

• Early stage of design , There should be a conscious separation of different layers , Create appearance patterns between layers .
• The development phase , Subsystems are becoming more and more complex , Add appearance mode to provide a simple calling interface .
• When maintaining a large legacy system , Maybe this system is very difficult to maintain and expand , But it also contains very important functions , Develop an appearance class for it , So that the new system can interact with it .

Code example

class API1:
def Save(self):
print(' Save the data A')
def Del(self):
print(' Delete data A')
class API2:
def Save(self):
print(' Save the data B')
def Del(self):
print(' Delete data B')
class Facade:
def __init__(self):
self._api1 = API1()
self._api2 = API2()
def SaveAll(self):
[obj.Save() for obj in [self._api1, self._api2]]
def DelAll(self):
[obj.Save() for obj in [self._api1, self._api2]]
if __name__ == '__main__':
test = Facade()
test.SaveAll()
test.DelAll()