An example of a reusable Django View

views.example.py

# This is not tested and not complete, but give an interesting example of how you can turn a Django view into something reusable.
# It is based on the code here: http://code.google.com/p/django-jqchat/
# It might make sense to turn this into an abstract base class.

# The purpose of this is:
# 1. Improved code reuse for outputting data.
# 2. Easier modification to relevant areas
# 3. Because it is new and interesting to me (Kiss my future jobs goodbye for admitting that :/)
# 4. Can stash it in a different file, so the view is not as cluttered-up.

# For example, you could define a class JsonExchange(ChatExchange) and make small modifications to output as JSON,
# an XMLExchange(ChatExchange) to do the same for XML, etc...  It seems far more reusable, although I could be wrong.

class ChatExchange(object):
    def authorize(self, request):
        # This is how we normally authorize the chat request.
        return request.user.is_authenticated()
    
    def invalid_login(self):
        return HttpResponseBadRequest('You need to be logged in to access the chat system.')
    
    def create_conversation(self, user1, user2):
        c = Conversation()
        c.name = "Conversation between %s and %s" % (str(user1), str(user2))
        c.distributor.add(user1)
        c.distributor.add(user2)
        c.save()
        return c

    # This retrieves the conversation
    def get_conversation(self):
        user1 = self.request.user.id
        user2 = user.objects.get(username=self.request.POST.get("to"))
        # find a conversation that has user1 and user2
        try:
            conversation = Conversation.objects.filter(distributor__id=user1.id).filter(distributor__id=user2.id)
            if conversation.open:
                self.conversation = conversation
                return
            elif Conversation.can_start_conversation(user1, user2):
                self.conversation = conversation
                return
        except:
            if Conversation.can_start_conversation(user1, user2):
                self.conversation = self.create_conversation(user1, user2)
                return
        self.conversation = False
    
    # This adds messages to the conversation.
    def add_messages(self):
        if "new_message" not in self.request.POST:
            return
        
        if not self.conversation:
            return

        user1 = self.request.POST.get("userid")
        m = Message()
        m.user = user1
        m.conversation = self.conversation
        m.text = self.request.POST.get("message")
        m.save()
        self.message = m
        self.statusCode = 2



    # This retrieves the messages in the conversation
    def get_messages(self):
        if not self.conversation:
            return
        self.messages = Message.objects.filter(conversation=self.conversation)
        self.statusCode = 1
    
    # An empty function that you can define to filter messages or perform any transformations necessary before output is made.
    def prehook(self):
        pass
    
    # An empty function that you can define to filter messages or perform any transformations necessary before output is made.
    def posthook(self):
        pass
    
    # Outputs messages in the format defined.  Must be overridden.
    def output_messages(self):
        raise NotImplementedError( "Should have implemented this" )
    
    # Outputs a success message if you want to override something or other.
    def output_success_message(self):
        raise NotImplementedError( "Should have implemented this" )
    
    # Outputs a list of errors in the program.
    def output_errors(self):
        raise NotImplementedError( "Should have implemented this" )

    def __call__(self, request):
        if not self.authorize(request):
            return self.invalid_login(request)
        self.statusCode = 0
        self.request = request
        self.prehook()
        self.get_conversation()
        self.add_messages()
        self.get_messages()
        self.posthook()

        if self.statusCode == 1:
            return self.output_messages()
        
        if self.statusCode == 2:
            return self.output_success_message()
        
        return self.output_errors()