Non-functional concept of the observer pattern for Twisted python objects using descriptors and metaclasses.

dataobject.py

lass DataObject(object):
    def to_html(self, updated_station):
        self.html = "whatever"
        self.on_html_update.callback(self.html)

    def update(self, updated_stations):
        self.json = self.to_json(updated_stations)
        self.on_json_update.callback(self.json)


class ObservableField(object):
    def __get__(self, instance, owner):
        # return deferred; wait what about sync clients? when to FIRE deferred?
    def __set__(self, instance, value):


class DataObjectMeta(object):
    def __new__(klass, name, bases, dct):
        # Itertate over ObservableField members and install descriptors
        # this is wrong
        for k,v in dict(dct).iteritems():
            if v isinstance(ObservableField):
                dct[k] = ObservableField._copy()
        return super(DataObjectMeta, klass).__new__(klass, name, bases, dct)
        # but maybe we should install event handlers here instead
        # e.g. on_html_update?


class DataObject(object):
    __metaclass__ = DataObjectMeta
    def on_update(self, observable_field, immediate=False):



class MyDataObject(DataObject):
    html = ObservableField()
    json = ObservableField()