python - 在 Django 模型中，外键字段如何知道与其他模型中的哪个字段匹配？

Question

我理解外键的作用，但我无法理解为什么它在 Django 中起作用。

我的项目模型位于“app1/models.py”文件中。该模型有一个名为“owner”的外键，它链接到我的“app2/models.py”文件中的 Profile 模型。

如果我只将模型名称传递给“所有者”字段，项目模型中的“所有者”字段如何知道它应该链接到配置文件模型中的“用户”字段？ 我觉得我应该在项目模型中传递 Profile.field 或类似的内容:

owner = models.ForeignKey(Profile.user, null=True, blank=True ... )

Dennis Ivy 教程中的完整模型代码:

class Profile(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE, null=True, blank=True)
    name = models.CharField(max_length=200, blank=True, null=True)
    email = models.EmailField(max_length=500, blank=True, null=True)
    username = models.CharField(max_length=200, blank=True, null=True)
    location = models.CharField(max_length=200, blank=True, null=True)
    short_intro = models.CharField(max_length=200, blank=True, null=True)
    bio = models.TextField(blank=True, null=True)
    profile_image = models.ImageField(
            null=True, blank=True, upload_to='profiles/', default='profiles/user-default.png')
    social_github = models.CharField(max_length=200, blank=True, null=True)
    social_twitter = models.CharField(max_length=200, blank=True, null=True)
    social_linkedin = models.CharField(max_length=200, blank=True, null=True)
    social_youtube = models.CharField(max_length=200, blank=True, null=True)
    social_website = models.CharField(max_length=200, blank=True, null=True)
    created = models.DateTimeField(auto_now_add=True)
    id = models.UUIDField(default=uuid.uuid4, unique=True, 
                            primary_key=True, editable=False)

class Project(models.Model):
    owner = models.ForeignKey(Profile, null=True, blank=True, on_delete=models.SET_NULL)
    title = models.CharField(max_length=200) #null is default=False and is required
    description = models.TextField(null=True, blank=True) #for a bigger field, allows null(for db)/blank(for Django get/post)
    featured_image = models.ImageField(null=True, blank=True, default='default.jpg')
    demo_link = models.CharField(max_length=2000)
    source_link = models.CharField(max_length=2000, null=True, blank=True) #can be blank in db
    tags = models.ManyToManyField('Tag', blank=True) #quotes will ref other class after this one 
    vote_total = models.IntegerField(default=0, null=True, blank=True)
    vote_ratio = models.IntegerField(default=0, null=True, blank=True)
    created = models.DateTimeField(auto_now_add=True) #generate when model instance is created
    id = models.UUIDField(default=uuid.uuid4, unique=True, primary_key=True, editable=False)

Answer 1

外键字段与另一个模型中的另一个字段不匹配。它与模型本身匹配。假设您想将名为“victor”的配置文件分配给新的项目模型对象，它会像这样:

from app_name.model import Project, Profile

profile1=Profile.objects.filter(name='victor').first()
new_project=Project(title='project 1',demolink='demo link',owner=profile1)

在这里，我们将用户对象分配给项目的所有者属性，而不是字段。

Profile.User 字段不是必需的。如果您想创建一个 customUser，我建议您应该查找一下，否则您会给自己带来许多身份验证问题。您必须为其创建一个模型管理器，然后才能开始自定义。它应该看起来像这样:

from django.db import models
from django.contrib.auth.models import User, AbstractUser
from django.utils.translation import ugettext_lazy as _
from django.contrib.auth.base_user import BaseUserManager


class CustomUserManager(BaseUserManager):
    """
    Custom user model manager where email is the unique identifiers
    for authentication instead of usernames.
    """
    def create_user(self, username, password, **extra_fields):
        """
        Create and save a User with the given username and password.
        """
        if not username:
            raise ValueError(_('The Username must be set'))
        user = self.model(username=username, **extra_fields)
        user.set_password(password)
        extra_fields.setdefault('is_staff', True)
        extra_fields.setdefault('is_superuser', False)
        extra_fields.setdefault('is_active', True)
        user.save()
        return user

    def create_superuser(self, username, password, **extra_fields):
        """
        Create and save a SuperUser with the given username and password.
        """
        extra_fields.setdefault('is_staff', True)
        extra_fields.setdefault('is_superuser', True)
        extra_fields.setdefault('is_active', True)

        if extra_fields.get('is_staff') is not True:
            raise ValueError(_('Superuser must have is_staff=True.'))
        if extra_fields.get('is_superuser') is not True:
            raise ValueError(_('Superuser must have is_superuser=True.'))
        return self.create_user(username, password, **extra_fields)

class Profile(AbstractUser):

    objects = CustomUserManager()
    name = models.CharField(max_length=200, blank=True, null=True)
    email = models.EmailField(max_length=500, blank=True, null=True)
    location = models.CharField(max_length=200, blank=True, null=True)
    short_intro = models.CharField(max_length=200, blank=True, null=True)
    bio = models.TextField(blank=True, null=True)
    profile_image = models.ImageField(
        null=True, blank=True, upload_to='profiles/', default='profiles/user-default.png')
    social_github = models.CharField(max_length=200, blank=True, null=True)
    social_twitter = models.CharField(max_length=200, blank=True, null=True)
    social_linkedin = models.CharField(max_length=200, blank=True, null=True)
    social_youtube = models.CharField(max_length=200, blank=True, null=True)
    social_website = models.CharField(max_length=200, blank=True, null=True)
    created = models.DateTimeField(auto_now_add=True)
    id = models.UUIDField(default=uuid.uuid4, unique=True, 
                        primary_key=True, editable=False)