django 在生成数据库表时报错： TypeError: __init__() missing 1 required positi...

版本：python: 3.6.4、django: 2.0
models.py 代码如下：

1. # coding: utf-8
   
2. from django.db import models
   
3. from django.contrib.auth.models import User
   
4. # Create your models here.
   
5. 
   
6. class Category(models.Model):
   
7.     name = models.CharField(max_length=100)
   
8. class Tag(models.Model):
   
9.     name = models.CharField(max_length=100)
   
10. class Post(models.Model):
    
11.     title = models.CharField(max_length=70)
    
12.     body = models.TextField()
    
13.     created_time = models.DateTimeField()
    
14.     modified_time = models.DateTimeField()
    
15.     excerpt = models.CharField(max_length=200, blank=True)
    
16.     category = models.ForeignKey(Category,on_delete=models.CASCADE)
    
17.     tags = models.ManyToManyField(Tag, blank=True)
    
18.     author = models.ForeignKey(User,on_delete=models.CASCADE)

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报错误信息如下图：

1. TypeError: __init__() missing 1 required positional argument: 'on_delete'

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中文翻译

1. TypeError：__init __（）缺少1个必需的位置参数：'on_delete'

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解决办法：

外键值的后面加上 on_delete=models.CASCADE

1. category = models.ForeignKey(Category)
   
2. author = models.ForeignKey(User)

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改为

1. category = models.ForeignKey(Category,on_delete=models.CASCADE)
   
2. author = models.ForeignKey(User,on_delete=models.CASCADE)
   

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