在 django 中复制模型实例效果不佳答案

【问题标题】：copy models instance in django not working well在 django 中复制模型实例效果不佳
【发布时间】：2021-09-10 20:44:43
【问题描述】：

我想复制 blogpost 模型，我已经考虑了外键关系，但在 blog_copy 和 blog_author_copy 的测试中仍然失败。谁能帮帮我？

class Author(models.Model):
    name = models.CharField(max_length=50)

class BlogPost(models.Model):
    title = models.CharField(max_length=250)
    body = models.TextField()
    author = models.ForeignKey(Author, on_delete=models.CASCADE, related_name='blog_posts')
    date_created = models.DateTimeField(auto_now_add=True)

    def copy(self):
        new = BlogPost.objects.get(pk=self.pk)
        new.pk = None
        new.id = None
        new.date_created = datetime.now()
        # new.author.blog_posts.add(new)
        authors = Author.objects.all()
        for author in authors:
            if self.author == author:
                author.blog_posts.add(new)
        new.save()
        old = BlogPost.objects.get(pk=self.pk)
        for comment in old.comments.all():
            comment.pk = None
            comment.blog_post = new
            comment.save()
            new.comments.add(comment)
            new.save()

class Comment(models.Model):
    blog_post = models.ForeignKey(BlogPost, on_delete=models.CASCADE, related_name='comments')
    text = models.CharField(max_length=500)

【问题讨论】：

标签： python django django-models copy deep-copy

【解决方案1】：

这可以这样实现：

    def copy(self):
        blog_copy = self
        blog_copy.pk = None
        blog_copy.id = None
        blog_copy.date_created = datetime.now()
        blog_copy.author = self.author
        blog_copy.save()

        comments_copy = []
        for comment in self.comments.all():
            comment.pk = None
            comment.id = None
            comment.blog_post = blog_copy
            comments_copy.append(comment)

        Comment.objects.bulk_create(comments_copy)
        return blog_copy

self 是实例本身，因此无需单独从数据库中获取。对于author，您可以使用self.author 获取当前的（comments 的想法相同）。

【讨论】：