Django snippets: RequestFetchingMixin

from django.http import HttpRequest

import inspect

class RequestFetchingMixin(object):
    def __new__(cls, *args, **kwargs):
        obj = object.__new__(cls, *args, **kwargs)
        f = inspect.currentframe()
        requests = []
        request = None
        backup_count = 0
        while not requests and f.f_back is not None and backup_count < 5:
            f = f.f_back
            for var, val in f.f_locals.iteritems():
                if isinstance(val, HttpRequest):
                    requests.append((var, val))
            backup_count += 1
        if not requests:
            request = None
        elif len(requests) == 1:
            request = requests[0][1]
        else:
            for var, val in requests:
                if var == 'request':
                    request = val
            if request is None:
                request = requests[0][1]
        obj.request = request
        return obj

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More a proof of concept than anything, this mixin addresses a perceived "shortcoming" of django forms: the inability to interact with the current request, and specifically the "current user".

Usage:

class SomeForm(forms.Form, RequestFetchingMixin):
  # fields...

  def __init__(self, *args, **kwargs):
    if self.request:
      # interact with self.request?
    super(SomeForm, self).__init__(*args, **kwargs)
    if self.request:
      # more interaction

  def clean(self):
    if self.request:
      # blah blah self.request.user blah

Notes:

This reaches "into the past" to pull an existing HttpRequest object, regardless of what name it was bound to, into "the present".
If multiple requests are found (what on earth are you doing??), the one bound to "request" (or the first one found, if that's not available) will be used.
By default it goes up to 5 frames back before giving up, but that can obviously be changed if you think you need it.
This won't work everywhere. self.request is guaranteed to be present, but may be None.
Just because you have a self.request doesn't mean self.request.user will be a valid user. This is subject to all the rules that a regular view's request is subject to (because it is a regular view's request!)
This isn't magic; it's just python.

Author:: eternicode
Posted:: January 26, 2011
Language:: Python
Django Version:: 1.2
Tags:: forms request mixin request.user
Score:: 0 (after 0 ratings)

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RequestFetchingMixin

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