創建一組Python類

Question

我有一個表示請求的類。我有一組非常具體的請求，比如「I-95」，「P-22」等，它們執行不同的功能並由控制器類調用。這樣做的最好方法是什麼，以便人們可以輕鬆地添加更多請求？

我有這樣的事情在此刻：

class Requests: 
    def __init__(self): 
      self.types = [ 
        'I-95', 
        'P-22', 
        ... 
      ] 

    def generate_request(self,type, Data): 
      # Here I would call the appropriate case for the type, e.g. P-22 

的請求的情況將是在它自己單獨的文件，並期待這樣的：

class P-22: 
    # Members 
    def __init__(self, Data): 
     # Set data members 
    def request(self): 
     # Submit request 

，我將能夠創建在控制器中的請求

f = Requests() 
f.generate_request('RC75') 

我正在努力做到乾淨，儘可能。謝謝！

Answer 1

試着這麼做：

class BaseRequest: 
    name = None 


class FooRequest(BaseRequest): 
    name = 'I-95' 

    def response(self): 
     return "foo" 


class BarRequest(BaseRequest): 
    name = 'P-22' 

    def response(self): 
     return "bar" 


class RequestManager: 

    def __init__(self): 
     self.requests = { 
      FooRequest.name: FooRequest, 
      BarRequest.name: BarRequest 
     } 

    def generate_request(self, name): 
     if name in self.requests: 
      return self.requests[name]() 

    def register_request(self, request_class): 
     assert issubclass(request_class, BaseRequest), \ 
      'Request class not a subclass of BaseRequest' 
     assert hasattr('name', request_class) and isinstance(request_class.name, str), \ 
      'Request name not correctly configured' 
     self.requests[request_class.name] = request_class 

然後：

manager = RequestManager() 
request = manager.generate_request('I-95') 
if request is not None: 
    print(request.response()) # "foo" 

而對於註冊新的要求：

class NewRequest(BaseRequest): 
    name = 'N-1' 

    def response(self): 
     return "new" 

manager = RequestManager() 
manager.register_request(NewRequest) 
request = manager.generate_request('N-1') 
if request is not None: 
    print(request.response()) # "new" 

我個人認爲這是一個使用了一個Singleton-pattern做得更好RequestManager（未經測試！）：

class RequestManager: 

    instance = None 

    class __RequestManager: 
     requests = { 
      FooRequest.name: FooRequest, 
      BarRequest.name: BarRequest 
     } 

     def generate_request(self, name): 
      if name in self.requests: 
       return self.requests[name]() 

     def register_request(self, request_class): 
      assert issubclass(request_class, BaseRequest), \ 
       'Request class not a subclass of BaseRequest' 
      assert hasattr('name', request_class) and isinstance(request_class.name, str), \ 
       'Request name not correctly configured' 
      self.requests[request_class.name] = request_class 

    def __new__(cls): 
     if not cls.instance: 
      cls.instance = cls.__RequestManager() 
     return cls.instance 

    @staticmethod 
    def getInstance(): 
     return RequestManager() 

這將創建一個靜態訪問RequestManager例如：

manager = RequestManager.getInstance() 
# Rest same as before, register some requests, etc. 

manager2 = RequestManager.getInstance() # This is actually the same manager ie. the same instance! 

manager和manager2共享相同的請求字典，所以更新通過其中一個適用於（從技術上來說，以同樣的經理，因爲您檢索相同的實例兩次）