Migrations Error in Django: AttributeError: 'str' object has no attribute '_meta' - python-3.x

Question

I know this has been asked before. But, I tried the available solutions. Those don't seem to work in my case unless I missed something unintentionally.
I dropped all the tables/relations from the connected database and deleted all the previous migration files except the init.py. And then ran the makemigrations command which worked fine. But got this error after running migrate.
Here is the error:
Applying book.0001_initial... OK
Applying reader.0001_initial...Traceback (most recent call last):
File "/home/brainiac77/github/bookworms_backend/backend/manage.py", line 22, in <module>
main()
File "/home/brainiac77/github/bookworms_backend/backend/manage.py", line 18, in main
execute_from_command_line(sys.argv)
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/core/management/__init__.py", line 446, in execute_from_command_line
utility.execute()
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/core/management/__init__.py", line 440, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/core/management/base.py", line 414, in run_from_argv
self.execute(*args, **cmd_options)
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/core/management/base.py", line 460, in execute
output = self.handle(*args, **options)
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/core/management/base.py", line 98, in wrapped
res = handle_func(*args, **kwargs)
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/core/management/commands/migrate.py", line 290, in handle
post_migrate_state = executor.migrate(
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/db/migrations/executor.py", line 131, in migrate
state = self._migrate_all_forwards(
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/db/migrations/executor.py", line 163, in _migrate_all_forwards
state = self.apply_migration(
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/db/migrations/executor.py", line 248, in apply_migration
state = migration.apply(state, schema_editor)
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/db/migrations/migration.py", line 131, in apply
operation.database_forwards(
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/db/migrations/operations/models.py", line 93, in database_forwards
schema_editor.create_model(model)
File "/home/brainiac77/Installations/anaconda3/lib/python3.9/site-packages/django/db/backends/base/schema.py", line 440, in create_model
if field.remote_field.through._meta.auto_created:
AttributeError: 'str' object has no attribute '_meta'
reader.0001_initial.py
# Generated by Django 4.0.6 on 2022-08-01 07:57
from django.conf import settings
from django.db import migrations, models
import django.db.models.deletion
class Migration(migrations.Migration):
initial = True
dependencies = [
migrations.swappable_dependency(settings.AUTH_USER_MODEL),
('book', '0001_initial'),
]
operations = [
migrations.CreateModel(
name='Reader',
fields=[
('rid', models.AutoField(primary_key=True, serialize=False)),
('photo_url', models.CharField(blank=True, max_length=200, null=True)),
('bio', models.CharField(blank=True, max_length=200, null=True)),
('read_books', models.ManyToManyField(through='reads.Reads', to='book.book')),
('user', models.OneToOneField(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL)),
],
options={
'db_table': 'reader',
},
),
]
Reader model
from django.db import models
from django.contrib.auth.models import User
class Reader(models.Model):
rid = models.AutoField(primary_key=True)
user = models.OneToOneField(User, on_delete=models.CASCADE)
photo_url = models.CharField(max_length=200, blank=True, null=True)
bio = models.CharField(max_length=200, blank=True, null=True)
read_books = models.ManyToManyField('book.Book', through='reads.Reads');
class Meta:
db_table = 'reader'
def __str__(self):
return {
'username': self.user.username,
'first_name': self.user.first_name,
'last_name': self.user.last_name,
'email': self.user.email,
'photo_url': self.photo_url,
'bio': self.bio,
}
Book Model
from django.db import models
from genre.models import Genre
from reader.models import Reader
class Book(models.Model):
isbn = models.CharField(max_length=13,primary_key=True)
title = models.CharField(max_length=255)
description = models.TextField()
photo_url = models.CharField(max_length=255)
page_count = models.IntegerField()
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
genres = models.ManyToManyField(Genre)
authors = models.ManyToManyField(Reader, related_name='authored_books')
class Meta:
db_table = 'book'
def __str__(self):
return {
'isbn': self.isbn,
'title': self.title,
'description': self.description,
'photo_url': self.photo_url,
'page_count': self.page_count,
'created_at': self.created_at,
'updated_at': self.updated_at,
'genres': self.genres.all(),
'authors': self.authors.all(),
}
Reads Model:
from django.db import models
from reader.models import Reader
from book.models import Book
class Reads(models.Model):
status_choices = (
('w', 'Want to Read'),
('r', 'Reading'),
('c', 'Completed'),
)
rsid = models.AutoField(primary_key=True)
reader = models.ForeignKey(Reader, on_delete=models.CASCADE)
book = models.ForeignKey(Book, on_delete=models.CASCADE)
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
status = models.CharField(max_length=1, choices=status_choices)
class Meta:
db_table = 'reads'
def __str__(self):
return {
'reader': self.reader.user.username,
'book': self.book.title,
'created_at': self.created_at,
'updated_at': self.updated_at,
'status': self.status,
}
INSTALLED_APPS
INSTALLED_APPS = [
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
# local apps
'rest_framework',
'rest_framework.authtoken',
'reader',
'book',
'genre',
'reads',
'bookreview',
'library',
'librarystock',
'bookborrow',
'friend',
]
What am I missing?

Answer 1

I think the migration file (reader.0001_initial.py) is wrong. There the foreign key table is book.book, which should be book.Book.
So I think you need to clear all the migration files and rerun the makemigrations command.
You can remake the migration file for the reader app using the following command.
python manage.py reset_migrations reader