Question

这是我的models.py文件：

from django.db import models


class Bus(models.Model):
    """bus details"""
    number_plate = models.CharField(max_length=9)

    def __str__(self):
        return self.number_plate


class BusStaff(models.Model):
    """details of the staff on each bus"""
    first_name = models.CharField(max_length=10)
    last_name = models.CharField(max_length=10)
    phone_number = models.CharField(max_length=10)
    bus = models.ForeignKey(Bus, on_delete=models.CASCADE, null=True)

    def __str__(self):
        return self.first_name, self.last_name


class Guardian(models.Model):
    """a model to hold the details of the child's guardian
    """
    first_name = models.CharField(max_length=20)
    last_name = models.CharField(max_length=20)
    phone_number = models.CharField(max_length=10)
    email = models.EmailField()

    def __str__(self):
        return self.first_name, self.last_name, self.phone_number


class Note(models.Model):
    """a model for holding the notes that Guardians and Staff can add notes (about delays) to the system.
    """
    title = models.CharField(max_length=100)
    description = models.TextField()

    # defined options for delays as a tuple
    reason_choices = (
        ('mech', "Bus mechanical failure"),
        ('delay_home', "Delayed at home(morning)"),
        ('delay_school', "Delayed at school(evening)"),
        ('traffic', "Road traffic jam"),
        ('emergency', "Emergency"),
    )

    # pick a reason from the tuple list defined above
    reason = models.CharField(choices=reason_choices, default='traffic', max_length=200)
    created_at = models.DateTimeField(auto_now_add=True)
    created_by_staff = models.ForeignKey(BusStaff, on_delete=models.CASCADE, null=True, blank=True)
    created_by_guardian = models.ForeignKey(Guardian, on_delete=models.CASCADE, null=True, blank=True)

    def __str__(self):
        return self.title, self.reason


class Student(models.Model):
    """holds the student details
    """

    first_name = models.CharField(max_length=20)
    last_name = models.CharField(max_length=20)
    school = models.CharField(max_length=50, help_text='Enter the name of the school')
    guardian = models.ForeignKey(Guardian, on_delete=models.CASCADE, null=True)

    def __str__(self):
        return self.first_name, self.last_name

这是我从运行迁移中获得的错误

D:\MyRideNotes>python manage.py migrate
System check identified some issues:

WARNINGS:
?: (1_8.W001) The standalone TEMPLATE_* settings were deprecated in Django 1.8 and the TEMPLATES dictionary takes precedence.
You must put the values of the following settings into your default TEMPLATES dict: TEMPLATE_DIRS.
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, notes, sessions
Running migrations:
  Applying notes.0003_auto_20180608_2041...Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\management\__init__.py", line 3
63, in execute_from_command_line
    utility.execute()
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\management\__init__.py", line 3
55, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\management\base.py", line 283,
in run_from_argv
    self.execute(*args, **cmd_options)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\management\base.py", line 330,
in execute
    output = self.handle(*args, **options)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\management\commands\migrate.py"
, line 204, in handle
    fake_initial=fake_initial,
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\migrations\executor.py", line 115
, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\migrations\executor.py", line 145
, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\migrations\executor.py", line 244
, in apply_migration
    state = migration.apply(state, schema_editor)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\migrations\migration.py", line 12
9, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\migrations\operations\fields.py",
 line 87, in database_forwards
    field,
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\backends\sqlite3\schema.py", line
 238, in add_field
    self._remake_table(model, create_field=field)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\backends\sqlite3\schema.py", line
 113, in _remake_table
    self.effective_default(create_field)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\backends\base\schema.py", line 22
9, in effective_default
    default = field.get_db_prep_save(default, self.connection)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\fields\related.py", line 9
63, in get_db_prep_save
    return self.target_field.get_db_prep_save(value, connection=connection)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\fields\__init__.py", line
770, in get_db_prep_save
    prepared=False)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\fields\__init__.py", line
958, in get_db_prep_value
    value = self.get_prep_value(value)
  File "C:\Users\vagabond\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\fields\__init__.py", line
966, in get_prep_value
    return int(value)
TypeError: int() argument must be a string, a bytes-like object or a number, not 'BusStaff'

可能是什么问题？

Answer 1

当您命名外键模型时，它必须是一个字符串。

你有：

bus = models.ForeignKey(Bus, on_delete=models.CASCADE, null=True)

正在寻找名为Bus的变量。

正确的格式是：

bus = models.ForeignKey(‘Bus’, on_delete=models.CASCADE, null=True)

您的所有外键似乎都不正确。

需要帮助在django模型中定义外键

1 个答案: