AttributeError：类型对象'Categories'在Django中没有属性'user_id__isnull'

Posted 2023-01-28

当我在Django中使用查询集时，出现此错误：

AttributeError：类型对象'Categories'没有属性'user_id__isnull'

The Categories模型在User模型上具有外键名为用户。

当我使用查询集：_Categories.objects.filter(Q(Categories.user_id__isnull==True ) | Q(user=user))_时，我本质上想做这样的事情：

SELECT * FROM Categories WHERE user_id=NULL | user.id=user.id 

（（user.id = user.id代表当前登录的用户）

forms.py：

from .models import Task, Categories
from django import forms
from django.forms import ModelForm
from django.db.models import Q

class TaskForm(ModelForm):

    task_title = forms.CharField(max_length=100)
    task_description = forms.CharField(widget=forms.Textarea)        
    due_date = forms.DateTimeField()    
    is_completed = forms.BooleanField()
    #categories = forms.ModelChoiceField(empty_label="---None---")

    class Meta:
        model = Task
        fields = ['task_title', 'task_description', 'due_date', 'is_completed', 'categories', 'parent']        

    def __init__(self, user, *args, **kwargs):
        # Get all the categories from the database for that specifc user
        super(TaskForm, self).__init__(*args, **kwargs)
        self.fields['categories'].queryset = Categories.objects.filter(Q(Categories.user_id__isnull==True ) | Q(user=user))        

models.py：

from django.db import models
from django.db.models import Q
from users.models import CustomUser
from django.urls import reverse
from django.contrib.auth import get_user_model


class Categories(models.Model):
    category_type = models.CharField(max_length=50)
    user = models.ForeignKey(CustomUser, null = True,  on_delete=models.CASCADE)

    def __str__(self):
        return '%s ' % (self.category_type)

    def get_absolute_url(self):
        return reverse('task_list')


class Task(models.Model):
    task_title = models.CharField(max_length=100)
    task_description = models.TextField()
    date_added =  models.DateTimeField(auto_now_add=True)
    due_date  = models.DateTimeField()
    is_completed = models.BooleanField(default=False)
    user = models.ForeignKey(get_user_model(), on_delete=models.CASCADE)

    categories = models.ForeignKey('Categories', on_delete=models.CASCADE)
    parent = models.ForeignKey("self", on_delete=models.CASCADE)

    class Meta:
        verbose_name = "Task"
        verbose_name_plural = "Tasks"

    def __str__(self):
        return '%s ID: %s' % (self.task_title, self.last_name)

    def get_absolute_url(self):
        return reverse('task_detail')

CustomUser模型：

from django.contrib.auth.models import AbstractUser
from django.db import models

class CustomUser(AbstractUser):
    nationality = models.CharField(null=True, blank=True, max_length=60)

答案

您的查询集语法错误。应该是：

Categories.objects.filter(Q(user_id__isnull=True) | Q(user=user))