mirror of
https://github.com/django/django.git
synced 2024-12-29 04:26:28 +00:00
8dde0504f3
CAST() must be wrapped in parentheses to be recognized as an expression on SQLite. Regression in7414704e88. Backport of797957fb48from main
71 lines
2.2 KiB
Python
71 lines
2.2 KiB
Python
"""
|
|
Callable defaults
|
|
|
|
You can pass callable objects as the ``default`` parameter to a field. When
|
|
the object is created without an explicit value passed in, Django will call
|
|
the method to determine the default value.
|
|
|
|
This example uses ``datetime.datetime.now`` as the default for the ``pub_date``
|
|
field.
|
|
"""
|
|
|
|
from datetime import datetime
|
|
from decimal import Decimal
|
|
|
|
from django.db import models
|
|
from django.db.models.functions import Coalesce, ExtractYear, Now, Pi
|
|
from django.db.models.lookups import GreaterThan
|
|
|
|
|
|
class Article(models.Model):
|
|
headline = models.CharField(max_length=100, default="Default headline")
|
|
pub_date = models.DateTimeField(default=datetime.now)
|
|
|
|
def __str__(self):
|
|
return self.headline
|
|
|
|
|
|
class DBArticle(models.Model):
|
|
"""
|
|
Values or expressions can be passed as the db_default parameter to a field.
|
|
When the object is created without an explicit value passed in, the
|
|
database will insert the default value automatically.
|
|
"""
|
|
|
|
headline = models.CharField(max_length=100, db_default="Default headline")
|
|
pub_date = models.DateTimeField(db_default=Now())
|
|
cost = models.DecimalField(
|
|
max_digits=3, decimal_places=2, db_default=Decimal("3.33")
|
|
)
|
|
|
|
class Meta:
|
|
required_db_features = {"supports_expression_defaults"}
|
|
|
|
|
|
class DBDefaults(models.Model):
|
|
both = models.IntegerField(default=1, db_default=2)
|
|
null = models.FloatField(null=True, db_default=1.1)
|
|
|
|
|
|
class DBDefaultsFunction(models.Model):
|
|
number = models.FloatField(db_default=Pi())
|
|
year = models.IntegerField(db_default=ExtractYear(Now()))
|
|
added = models.FloatField(db_default=Pi() + 4.5)
|
|
multiple_subfunctions = models.FloatField(db_default=Coalesce(4.5, Pi()))
|
|
case_when = models.IntegerField(
|
|
db_default=models.Case(models.When(GreaterThan(2, 1), then=3), default=4)
|
|
)
|
|
|
|
class Meta:
|
|
required_db_features = {"supports_expression_defaults"}
|
|
|
|
|
|
class DBDefaultsPK(models.Model):
|
|
language_code = models.CharField(primary_key=True, max_length=2, db_default="en")
|
|
|
|
|
|
class DBDefaultsFK(models.Model):
|
|
language_code = models.ForeignKey(
|
|
DBDefaultsPK, db_default="fr", on_delete=models.CASCADE
|
|
)
|