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django/tests/modeltests/expressions/models.py
Russell Keith-Magee cf37e4624a Fixed #7210 -- Added F() expressions to query language. See the documentation for details on usage.
Many thanks to:
    * Nicolas Lara, who worked on this feature during the 2008 Google Summer of Code.
    * Alex Gaynor for his help debugging and fixing a number of issues.
    * Malcolm Tredinnick for his invaluable review notes.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@9792 bcc190cf-cafb-0310-a4f2-bffc1f526a37
2009-01-29 10:46:36 +00:00

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2.4 KiB
Python

"""
Tests for F() query expression syntax.
"""
from django.db import models
class Employee(models.Model):
firstname = models.CharField(max_length=50)
lastname = models.CharField(max_length=50)
def __unicode__(self):
return u'%s %s' % (self.firstname, self.lastname)
class Company(models.Model):
name = models.CharField(max_length=100)
num_employees = models.PositiveIntegerField()
num_chairs = models.PositiveIntegerField()
ceo = models.ForeignKey(
Employee,
related_name='company_ceo_set')
point_of_contact = models.ForeignKey(
Employee,
related_name='company_point_of_contact_set',
null=True)
def __unicode__(self):
return self.name
__test__ = {'API_TESTS': """
>>> from django.db.models import F
>>> Company(name='Example Inc.', num_employees=2300, num_chairs=5,
... ceo=Employee.objects.create(firstname='Joe', lastname='Smith')).save()
>>> Company(name='Foobar Ltd.', num_employees=3, num_chairs=3,
... ceo=Employee.objects.create(firstname='Frank', lastname='Meyer')).save()
>>> Company(name='Test GmbH', num_employees=32, num_chairs=1,
... ceo=Employee.objects.create(firstname='Max', lastname='Mustermann')).save()
# We can filter for companies where the number of employees is greater than the
# number of chairs.
>>> Company.objects.filter(num_employees__gt=F('num_chairs'))
[<Company: Example Inc.>, <Company: Test GmbH>]
# The relation of a foreign key can become copied over to an other foreign key.
>>> Company.objects.update(point_of_contact=F('ceo'))
3
>>> [c.point_of_contact for c in Company.objects.all()]
[<Employee: Joe Smith>, <Employee: Frank Meyer>, <Employee: Max Mustermann>]
>>> c = Company.objects.all()[0]
>>> c.point_of_contact = Employee.objects.create(firstname="Guido", lastname="van Rossum")
>>> c.save()
# F Expressions can also span joins
>>> Company.objects.filter(ceo__firstname=F('point_of_contact__firstname')).distinct()
[<Company: Foobar Ltd.>, <Company: Test GmbH>]
>>> _ = Company.objects.exclude(ceo__firstname=F('point_of_contact__firstname')).update(name='foo')
>>> Company.objects.exclude(ceo__firstname=F('point_of_contact__firstname')).get().name
u'foo'
>>> _ = Company.objects.exclude(ceo__firstname=F('point_of_contact__firstname')).update(name=F('point_of_contact__lastname'))
Traceback (most recent call last):
...
FieldError: Joined field references are not permitted in this query
"""}