Django选择。 如何设置一个只能选择一次的选项

Question

I am working on a blog. I have a section where there will be a special post. And another page where I have collection of special posts. Here is my model.py

class Post(models.Model):
    post = models.TextField()
    SPECIAL = (
        ('0', 'Special Post'),
        ('1', 'General Post'),
        ('2', 'Inactive Special Post'),
    )
    specialpost = models.CharField(max_length=1, choices=SPECIAL, default='1', )

Only One post should be in the Special Post. When new special post is added, the old special post should be shifted to Inactive Special Post. So it can be shown in the Collection of Special post page. How can I do this?

Answer 1

As @neeraj-kumar mentioned in comment, you can achieve this by overriding model's save() method. Add to Post class something like this:

class Post(models.Model):
    ...

    def save(self, *args, **kwargs):
        special_post = Post.objects.filter(specialpost='0')
        if self.specialpost == '0' and special_post:
            special_post.update(specialpost='2')
        super(Post, self).save(*args, **kwargs)

Answer 2

when you add a new post, filter the query like this change_actual_post = Post.objects.get(specialpost=0) and then change the status of your old post change_actual_post.specialpost = 2 finally save change_actual_post.save() .

Add these 3 lines into your views.py file before add a new special post