Django snippets: PreSaveMiddleware

from django.dispatch import dispatcher
from django.db.models import signals

PRE_SAVE_REQUEST = None

class PreSaveMiddleware(object):
    """ 
    This bit of middleware just saves the request in a global variable
    that can be used to pass the request on to any pre_save methods in
    your models
    """

    def process_request(self, request):
        global PRE_SAVE_REQUEST
        PRE_SAVE_REQUEST = request

def pre_save(**kwargs):
    instance  = kwargs['instance']
    if getattr(instance, 'pre_save', None):
        instance.pre_save(PRE_SAVE_REQUEST)

dispatcher.connect(pre_save, signal=signals.pre_save)

With this middleware in place (add it to the MIDDLEWARE_CLASSES in your settings) you can pass a request to the model via a pre_save method on the model.

I'm not sure if it is an improvement over the threadlocals method but it may be an alternative that can be improved upon?

class MyModel(models.Model):
    name = models.CharField(max_length=50)
    created = models.DateTimeField()
    created_by = models.ForeignKey(User, null=True, blank=True)

    def pre_save(self, request):
        if not self.id:
            self.created_by = request.user

Author:: pterk
Posted:: November 20, 2007
Language:: Python
Tags:: middleware pre_save signals
Score:: 2 (after 2 ratings)

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