A Django like messages framework for Tornado
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This document introduces a simple messages framework for Tornado based on Django's messages framework. It allows flashing messages to users after certain actions. The key points are: 1) Messages are stored in cookies to prevent them from being lost on page redirects or reloads. 2) A Message object is created for each request to store messages in a request property. 3) On redirects, the Message object updates the cookies to write any new messages or clear old ones. 4) A template tag iterates through the messages and displays them, clearing the messages from the cookies.
![Easy Solution
def prepare(self):
# Define a message array as a property of each
# request, and just append every message to
# it.
self.request.messages = []
!
def MyHandler(tornado.web.RequestHandler):
def get(self):
self.request.messages.append("error")
return self.render("my_page.html")](https://image.slidesharecdn.com/tornadomessagesframework-140315235421-phpapp01/85/A-Django-like-messages-framework-for-Tornado-9-320.jpg)
![Message Insight
!
!
class FlashMessage(object):
"""
A Django messages framework mockup, use cookie to store messages.
"""
…
!
def __iter__(self):
self.used = True
if self._queued_messages:
self._loaded_messages.extend(self._queued_messages)
self._queued_messages = []
# Update messages stored in Cookie
self.update_messages()
return iter(self._loaded_messages)
!
def update_messages(self):
if self.used:
self._store(self._queued_messages)
elif self.added_new:
messages = self._loaded_messages + self._queued_messages
self._store(messages)
!
def _update_cookie(self, encoded_data):
if encoded_data and eval(encoded_data or ''):
self._handler.set_secure_cookie(self.cookie_name, encoded_data,
expires_days=None,
domain=settings.SESSION_COOKIE_DOMAIN)
else:
self._handler.clear_cookie(self.cookie_name,
domain=settings.SESSION_COOKIE_DOMAIN)
!
def _store(self, messages):
encoded_data = self._encode(messages)
# Update cookie, remove if no data included.
self._update_cookie(encoded_data)](https://image.slidesharecdn.com/tornadomessagesframework-140315235421-phpapp01/85/A-Django-like-messages-framework-for-Tornado-17-320.jpg)
A Django like messages framework for Tornado
- 1. Introduction to a simple messages framework for Tornado Gao Chao 2014.03.14
- 2. Tornado • A high performance asynchronous web framework. • Originated in FriendFeed, acquired by Facebook later on. • We are using it!
- 3. Messages Framework • Taken from Django’s messages framework. • Flash a message after certain actions by user.
- 5. Design concern • Easy to use and simple implementation. • Messages cannot be dropped on redirection. • All unseen messages need to be displayed.
- 7. Messages Lifetime • Request coming in. • Server execute an action based on passed parameters. • Server popup a message to user. • User sees the web page and the message.
- 8. Hook • def prepare(self) • def render(self, template_name, **kwargs)
- 9. Easy Solution def prepare(self): # Define a message array as a property of each # request, and just append every message to # it. self.request.messages = [] ! def MyHandler(tornado.web.RequestHandler): def get(self): self.request.messages.append("error") return self.render("my_page.html")
- 12. Solution • Save messages in cookies • Clear messages only after user has seen.
- 13. How? • def redirect(self, url, permanet=False, status=None) • def __iter__(self)
- 14. HTML {% if messages %} <ul class="messages"> {% for message in messages %} <li>{{ message }}</li> {% end %} </ul> {% end %}
- 15. Clear • We can erase all messages stored in cookies after __iter__ method of Message object was called. • We don’t need to update cookies when there is no redirections happen.
- 16. To sum up class BaseHandler(tornado.web.RequestHandler): def prepare(self): # Create Message object in order to store instant messages. self.messages = FlashMessage(handler=self) ! def redirect(self, url, permanent=False, status=None): if hasattr(self, "messages"): # Update messages in Cookie, write in or clear all. self.messages.update_messages() ! ! class LoginHandler(BaseHandler): def post(self): # Write message to object owned structure. messages.success(self.messages, "Login successfully!") ! # Redirect to another handler. self.redirect("/")
- 17. Message Insight ! ! class FlashMessage(object): """ A Django messages framework mockup, use cookie to store messages. """ … ! def __iter__(self): self.used = True if self._queued_messages: self._loaded_messages.extend(self._queued_messages) self._queued_messages = [] # Update messages stored in Cookie self.update_messages() return iter(self._loaded_messages) ! def update_messages(self): if self.used: self._store(self._queued_messages) elif self.added_new: messages = self._loaded_messages + self._queued_messages self._store(messages) ! def _update_cookie(self, encoded_data): if encoded_data and eval(encoded_data or ''): self._handler.set_secure_cookie(self.cookie_name, encoded_data, expires_days=None, domain=settings.SESSION_COOKIE_DOMAIN) else: self._handler.clear_cookie(self.cookie_name, domain=settings.SESSION_COOKIE_DOMAIN) ! def _store(self, messages): encoded_data = self._encode(messages) # Update cookie, remove if no data included. self._update_cookie(encoded_data)
- 18. Read the source code to get more of it!
- 19. Thank you!