Django: set model choice field options to queryset values and other value - django

Question

In the below Django models
class Post(models.Model):
author = models.ForeignKey(CustomUser, on_delete=models.CASCADE,)
title = models.CharField(max_length=200, null=True)
text = models.TextField()
post_url = models.URLField(max_length = 200, blank=True)
post_type = models.IntegerField()
slug = models.SlugField(unique=True, blank=True)
class Tiers(models.Model):
user = models.ForeignKey(CustomUser, default=None, null=True, on_delete=models.CASCADE,)
tier_name = models.CharField(max_length=128, blank=True)
tier_value = models.IntegerField()
slug = models.SlugField(unique=True, blank=True)
I want to use post model for a form like below
class PostForm(forms.ModelForm):
class Meta:
model = models.Post
fields = ('title', 'text', 'post_url', 'post_type')
But for post_type field I want to display as dropdown with options from Tiers models tier_value. For example if user1 has 3 entries in Tiers model with tier_values as 10, 20 and 30. I want to display 4 options 0, 10, 20 , and 30. Can someone help me how to achieve this?

Answer 1

In theory, you can override the FormField django generates. In this case, you could use a Select widget for the post_type field.
However, I think with your modeling can be improved/normalized, and if that is done, your issue will resolve. Consider these models:
class Tier(models.Model):
name = models.CharField(max_length=128, blank=True)
value = models.IntegerField()
slug = models.SlugField(unique=True, blank=True)
class CustomUser(...):
tiers = models.ManyToManyField(Tier, related_name='users')
...
class Post(models.Model):
author = models.ForeignKey(CustomUser, on_delete=models.CASCADE)
tier = models.ForeignKeyField(Tier)
title = models.CharField(max_length=200, null=True)
text = models.TextField()
url = models.URLField(max_length = 200, blank=True)
slug = models.SlugField(unique=True, blank=True)
This way, you different users can have the same tier (which is probably what you want?) without duplication of the name and level values.
Now, when you create ModelForm with Post, it will automatically give you select field for all existing tiers. However, you just want to be able to select the tiers the user is in, so you would set a custom queryset for that field:
class PostForm(forms.ModelForm):
def __init__(self, user, *args, **kwargs):
super().__init__(*args, **kwargs)
self.fields['tier'].queryset = Tier.objects.filter(users__in=[user])
class Meta:
model = models.Post
fields = ('title', 'text', 'url', 'tier')
Edit: I just now saw that you want to allow all tiers that the user is in or that have less value. You can do this the same way, you just have to adapt the queryset:
max_tier_value = user.tiers.aggregate(Max('value')).value__max
self.fields['tier'].queryset = Tier.objects.filter(value__lte=max_tier_value)
However, you probably want to do either of these two, but not both:
Each user is assigned with a tier level and can create posts with any lower tier level.
Each user is assigned with multiple tier levels and can only create posts with these.
So, if you go with this queryset, you should remodel so that CustomUser.tier is a models.ForeignKey(Tier, related_name='users')