Post made up of blocks (text, image, video) - django

Question

I'm trying to create a image site with a similar form for adding posts as on Imgur. A post should be made up of unlimited number of blocks of various types (text, image, video) that create finished blog post.
User chooses with which block he wants to start (maybe upload an image) and then adds another block by clicking a button.
I can't figure out a sensible model for blocks that would make up a single post.
This is my Post model:
class Post(models.Model):
author = models.ForeignKey('auth.User')
text = models.TextField() #just a placeholder until blocks work
created_date = models.DateTimeField(
default=timezone.now)
isWaiting = models.BooleanField(default=True)
isLocked = models.BooleanField(default=False)
views = models.IntegerField(default=0)
tags = TaggableManager(help_text="")
I don't know if I should define separate models for textblock, imageblock and videoblock (all with ForeignKey to Post model) or if there's a better solution.
I thought of a universal model that would store a TextField (for text written by the user) and a FileField (for image and video upload) used for every block type but one of the Fields in every record would always be empty (user can only write text or upload a file per block) and it seems like a "waste of space".
I appreciate any ideas for solving this problem.

Answer 1

If anyone comes across a similar problem I chose a universal content block design with many fields (some are empty depending on a block type, ex. media is empty when adding text block). It was easier for me to implement and later add necessary JS for dynamically adding more PostBlocks to Post.
Relevant models:
class Post(models.Model):
author = models.ForeignKey('auth.User')
title = models.CharField(max_length=100)
slug = models.SlugField(unique=True)
created_date = models.DateTimeField(default=timezone.now)
views = models.IntegerField(default=0)
tags = TaggableManager(help_text="")
class PostBlock(models.Model):
POST_TYPE_CHOICES = (
('TXT', 'Text'),
('IMG', 'Image'),
('VID', 'Video'),
)
postid = models.ForeignKey('Post', on_delete=models.CASCADE)
text = models.TextField(max_length=1024, blank=True)
media = models.FileField(upload_to=content_path, blank=True, validators=[
validate_file_extension])
contenttype = models.CharField(
max_length=3,
choices=POST_TYPE_CHOICES,
default='IMG',
)
order = models.IntegerField(default=0)
One Post can have as many PostBlocks as you need.