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"""
Many-to-one relationships
To define a many-to-one relationship, use ``ForeignKey()``.
"""
from django.db import models
class Reporter(models.Model):
first_name = models.CharField(max_length=30)
last_name = models.CharField(max_length=30)
email = models.EmailField()
def __str__(self):
return "%s %s" % (self.first_name, self.last_name)
class Article(models.Model):
headline = models.CharField(max_length=100)
pub_date = models.DateField()
reporter = models.ForeignKey(Reporter, models.CASCADE)
class Meta:
ordering = ("headline",)
def __str__(self):
return self.headline
class Country(models.Model):
id = models.SmallAutoField(primary_key=True)
name = models.CharField(max_length=50)
class City(models.Model):
id = models.BigAutoField(primary_key=True)
country = models.ForeignKey(
Country, models.CASCADE, related_name="cities", null=True
)
name = models.CharField(max_length=50)
class District(models.Model):
city = models.ForeignKey(City, models.CASCADE, related_name="districts", null=True)
name = models.CharField(max_length=50)
def __str__(self):
return self.name
# If ticket #1578 ever slips back in, these models will not be able to be
# created (the field names being lowercased versions of their opposite classes
# is important here).
class First(models.Model):
second = models.IntegerField()
class Second(models.Model):
first = models.ForeignKey(First, models.CASCADE, related_name="the_first")
# Protect against repetition of #1839, #2415 and #2536.
class Third(models.Model):
name = models.CharField(max_length=20)
third = models.ForeignKey(
"self", models.SET_NULL, null=True, related_name="child_set"
)
class Parent(models.Model):
name = models.CharField(max_length=20, unique=True)
bestchild = models.ForeignKey(
"Child", models.SET_NULL, null=True, related_name="favored_by"
)
class ParentStringPrimaryKey(models.Model):
name = models.CharField(primary_key=True, max_length=15)
class Child(models.Model):
name = models.CharField(max_length=20)
parent = models.ForeignKey(Parent, models.CASCADE)
class ChildNullableParent(models.Model):
parent = models.ForeignKey(Parent, models.CASCADE, null=True)
class ChildStringPrimaryKeyParent(models.Model):
parent = models.ForeignKey(ParentStringPrimaryKey, on_delete=models.CASCADE)
class ToFieldChild(models.Model):
parent = models.ForeignKey(
Parent, models.CASCADE, to_field="name", related_name="to_field_children"
)
# Multiple paths to the same model (#7110, #7125)
class Category(models.Model):
name = models.CharField(max_length=20)
def __str__(self):
return self.name
class Record(models.Model):
category = models.ForeignKey(Category, models.CASCADE)
class Relation(models.Model):
left = models.ForeignKey(Record, models.CASCADE, related_name="left_set")
right = models.ForeignKey(Record, models.CASCADE, related_name="right_set")
def __str__(self):
return "%s - %s" % (self.left.category.name, self.right.category.name)
# Test related objects visibility.
class SchoolManager(models.Manager):
def get_queryset(self):
return super().get_queryset().filter(is_public=True)
class School(models.Model):
is_public = models.BooleanField(default=False)
objects = SchoolManager()
class Student(models.Model):
school = models.ForeignKey(School, models.CASCADE)
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