Django - 创建模型的子模型

Question

I want to create submodels(I do not know if this is the correct term to use) of a model. For example, let's say I have a model called Post . But I want this model's fields changable by users. Like users select their Post type. Right now I want to create a two different types: first is a

class TextBasedPost(models.Model):
    title = models.CharField(max_length=100)
    content = RichTextField() # which has been imported from ckeditor.fields
    author = models.ForeignKey(User, on_delete=models.CASCADE)
    datePosted = models.DateTimeField(default=timezone.now)

    def __str__(self):
        return self.title

    def get_absolute_url(self):
        return reverse('post_detail',kwargs={'pk':self.pk})

Other one is a post with only image attachment:

class ImageBasedPost(models.Model):
    title = models.CharField(max_length=100)
    image_attachment = models.ImageField(default='default.png', upload_to='profile_pics') # there will not be a usage of default.png
    author = models.ForeignKey(User, on_delete=models.CASCADE)
    datePosted = models.DateTimeField(default=timezone.now)

    def crop_image(self):
        img = Image.open(self.image.path) # Image imported from PIL

        if img.height > 600 or img.width > 600:
            output_size = (600,600)
            img.thumbnail(output_size)
            img.save(self.image_attachment.path)

    def __str__(self):
        return self.title

    def get_absolute_url(self):
        return reverse('post_detail',kwargs={'pk':self.pk})

But like you see this is not good way to use since there are same fields and same functions in both models(only one fields and one function is different). But this is not a good practice. So is there a way to do this with better way?

Answer 1

the best approach is to create an abstract parent model and put all shared fields inside of it. then inherit your models from it, and add the fields you wants to any of them. you will then be able to override your methods inside the child models:

class GenericPost(models.Model):
    title = models.CharField(max_length=100)
    author = models.ForeignKey(User, on_delete=models.CASCADE)
    datePosted = models.DateTimeField(default=timezone.now)


    class Meta:
        abstract = True

    def __str__(self):
        return self.title

    def get_absolute_url(self):
        return reverse('post_detail',kwargs={'pk':self.pk})

class TextBasedPost(GenericPost):
    content = RichTextField() # which has been imported from ckeditor.fields
    
class ImageBasedPost(GenericPost):
    image_attachment = models.ImageField(default='default.png', upload_to='profile_pics') # there will not be a usage of default.png

    def crop_image(self):
        img = Image.open(self.image.path) # Image imported from PIL

        if img.height > 600 or img.width > 600:
            output_size = (600,600)
            img.thumbnail(output_size)
            img.save(self.image_attachment.path)

learn more here: https://docs.djangoproject.com/en/3.1/topics/db/models/#abstract-base-classes