改写model的save()方法

from django.db import models
from django.utils.html import strip_tags

class Blog(models.Model):
    title = models.CharField(max_length=70,blank=True, default='')
    code = models.TextField()
    created = models.DateTimeField(auto_now_add=True)
    excerpt = models.CharField(max_length=200,blank=True)  # 摘要

    def __str__(self):
       return self.title
    
    def save(self, *args, **kwargs):
       if not self.excerpt:
           self.excerpt = strip_tags(self.body)[:50]
       super().save(*args, **kwargs)