在Django中自动用FK向用户填充模型字段

Question

I have this small models.py file:

models.py

# -*- coding: utf-8 -*-
import datetime

from django.db import models
from django.contrib.auth.models import User

from apps.strumento.models import Strumento, Veicolo

class AllegatoStrumento(models.Model):
    allegato = models.FileField(upload_to='uploads_strumento/', blank=True, null=True)
    data_creazione = models.DateTimeField(default=datetime.datetime.now)
    creatore = models.ForeignKey(User)
    strumento = models.ForeignKey(Strumento)

    class Meta:
        verbose_name_plural = "Allegati strumenti"
        verbose_name = "Allegato strumento"

    def __unicode__(self):
        return str(self.allegato)

I would like the 'creatore' field to be automatically populated with the logged user triggering the save/update action, so that I can display it but not allow it to be altered directly.

OF course, just putting the User FK like this in the model, it asks me which user to put in, which I don't want to happen.

I've tried with both these lines:

creatore = models.ForeignKey(User, default=request.user.get_username())
creatore = models.ForeignKey(User, default=User.get_username())

but none of them work, as the first misses an instance of request while the second complains that the method is NOT (corrected, thanks @bruno desthuilliers) being called on an instance (" TypeError: unbound method get_username() must be called with User instance as first argument (got nothing instead) ")

What could an easy way for doing that be?

Answer 1

The fact that models don't have a "magical" access to the "current request" is by design - because there's not necessarily such a thing as a "current request", ie when working on your models from a command-line script etc.

The correct way to handle the problem is to explicitely pass in the "current user" from your views (which get the request as first argument).

As a side note

1. your implementation of AllegatoStrumento.__unicode__ is broken ( __unicode__ must return a unicode object, not a str object - hint: all text fields in django models return unicode)

2. your second attempt at providing a default in the model itself complains that get_username() is not called on an instance

3. anyway, your field expects a User instance, not a username so the call to get_username() is way off mark.