Adapter pattern works as a bridge between two incompatible interfaces. This type of design pattern comes under structural pattern as this pattern combines the capability of two independent interfaces.
This pattern involves a single class, which is responsible to join functionalities of independent or incompatible interfaces. A real life example could be the case of a card reader, which acts as an adapter between memory card and a laptop. You plug in the memory card into the card reader and the card reader into the laptop so that memory card can be read via the laptop.
The adapter design pattern helps to work classes together. It converts the interface of a class into another interface based on requirement. The pattern includes a speciation a polymorphism which names one name and multiple forms. Say for a shape class which can use as per the requirements gathered.
There are two types of adapter pattern −
This design pattern relies on object implementation. Hence, it is called the Object Adapter Pattern.
This is an alternative way to implement the adapter design pattern. The pattern can be implemented using multiple inheritances.
Let us now see how to implement the adapter pattern.
class EuropeanSocketInterface: def voltage(self): pass def live(self): pass def neutral(self): pass def earth(self): pass # Adaptee class Socket(EuropeanSocketInterface): def voltage(self): return 230 def live(self): return 1 def neutral(self): return -1 def earth(self): return 0 # Target interface class USASocketInterface: def voltage(self): pass def live(self): pass def neutral(self): pass # The Adapter class Adapter(USASocketInterface): __socket = None def __init__(self, socket): self.__socket = socket def voltage(self): return 110 def live(self): return self.__socket.live() def neutral(self): return self.__socket.neutral() # Client class ElectricKettle: __power = None def __init__(self, power): self.__power = power def boil(self): if self.__power.voltage() > 110: print "Kettle on fire!" else: if self.__power.live() == 1 and \ self.__power.neutral() == -1: print "Coffee time!" else: print "No power." def main(): # Plug in socket = Socket() adapter = Adapter(socket) kettle = ElectricKettle(adapter) # Make coffee kettle.boil() return 0 if __name__ == "__main__": main()
The above program generates the following output −
The code includes adapter interface with various parameters and attributes. It includes Adaptee along with Target interface that implements all the attributes and displays the output as visible.