Tornado Get Reference to Instance Variable in RequestHandler

Question

In writing a tornado Http Server, I am having trouble with accessing an instance variable in my main class, which contains the tornado application object as well as start method, from a separate RequestHandler object. Consider the following crude example,

class MyServer(object):

    def __init__(self):
        self.ref_object = 0 
        self.application = #Add tornado.web.applicaiton here

    def change_ref_object(self, ref_obj):
        self.ref_object = ref_obj

    def start(self):
        #start the server
        pass

class SomeHandler(tornado.web.RequestHandler):

    def post(self):
        #Yada, yada, yada

        #Call method on Myserver's ref_object
        pass

I need to access the ref_object instance of MyServer in the post() method of SomeHandler and I need to make sure that the ref_object accessed in SomeHandler is the same object if its changed in change_ref_object().

Somehandler is only referenced as a class when creating a python tornado web server (application), and it isn't clear how one would access such an instance of SomeHandler to change its temporary ref_object when its changed in MyServer.

It basically comes down to me not understanding where the instances of SomeHandler would exist within the scope of MyServer (or specifically, MyServer's application object).

Answer 1

When you create your Application object, you can pass your ref_object instance to SomeHandler by placing it in a dict as a third argument to the tuple normally used to define the handler. So, in MyServer.__init__:

self.application = tornado.web.Application([
    (r"/test", SomeHandler, {"ref_object" : self.ref_object}),
])

Then add an initialize method to SomeHandler:

class SomeHandler(tornado.web.RequestHandler):
    def initialize(self, ref_object):
        self.ref_object = ref_object

    def post(self):
       self.ref_object.method()