best way to implement ManyToManyField check? - django

Question

Want to create a Song object. How do I check if this Song object is in a particular user's UserProfile to avoid repetition?
tried this but threw me an error argument of type 'QuerySet' is not iterable;
songs_available = user.userprofile.liked_songs.all()
if not song in songs_available:
user.userprofile.liked_songs.add(song)
models.py
class Song(models.Model):
track_name = models.CharField(max_length=250)
artiste_name= models.CharField(
max_length=200)
album = models.ForeignKey(Album, on_delete= models.CASCADE, null=True, default=None, related_name =
"songs")
class Meta:
db_table="Song"
def __str__(self):
return self.track_name
class UserProfile(models.Model):
user = models.OneToOneField(User, on_delete=models.CASCADE, default=None , null= True)
liked_songs = models.ManyToManyField("Song", null=True , default=None,
related_name="users_that_liked_me")
class Meta:
db_table = "UserProfile"
def __str__(self):
return self.user.username
views.py (part of it)
song, created = Song.objects.get_or_create(track_name = track,
artiste_name = artist,
album = album)
wanted to try if created but that only checks for the song model as many users could have the same song, it doesnt really help

Answer 1

You can do this, because I have improved your code
class Song(models.Model):
track_name = models.CharField(max_length=250)
artiste_name= models.CharField(
max_length=200)
album = models.ForeignKey(Album, on_delete= models.CASCADE, null=True,
related_name="songs")
class UserProfile(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE, null= True)
liked_songs = models.ManyToManyField("Song"related_name="users_that_liked_me")

Answer 2

refer to Django's docs for many-to-many field management.
here you can't directly add a many-to-many fields.
first, you need to create an object then add many-to-many data to it.
https://docs.djangoproject.com/en/3.1/topics/db/examples/many_to_many/

Answer 3

So according to the Django Docs, as #iklinac stated in the comments, .add() prevents duplicate creation when populating a many to many field, as in my case. Eventually solved the problem like this.
song, created = Song.objects.get_or_create(track_name = track,
artiste_name = artist,
album = album)
user.userprofile.liked_songs.add(song)
All other code in my question remains the same.