Django snippets

from django.db import models


class Review(models.Model):
    LOW_RATING = 1
    AVERAGE_RATING = 2
    HIGH_RATING = 3
    RATING_CHOICES = (
        (LOW_RATING, 'Low'),
        (AVERAGE_RATING, 'Average'),
        (HIGH_RATING, 'High'),
        )
    title = models.CharField(max_length=250)
    pub_date = models.DateTimeField()
    body = models.TextField()
    rating = models.IntegerField(choices=RATING_CHOICES)


class ReviewedObjectManager(models.Manager):
    def _get_review_field(self):
        if not hasattr(self, '_review_field'):
            for f in self.model._meta.fields:
                if f.rel and f.rel.to == Review:
                    setattr(self, '_review_field', f.name)
                    break
        return self._review_field
    
    def rating_equals(self, rating):
        review_field = self._get_review_field()
        return self.filter(**{ '%s__rating' % review_field: rating })


class Movie(models.Model):
    title = models.CharField(max_length=255)
    description = models.TextField()
    running_time = models.PositiveIntegerField()
    movie_review = models.ForeignKey(Review)
    
    objects = ReviewedObjectManager()


class Restaurant(models.Model):
    name = models.CharField(max_length=255)
    address = models.CharField(max_length=255)
    description = models.TextField()
    restaurant_review = models.ForeignKey(Review)
    
    objects = ReviewedObjectManager()