Hello i have registered models like that

# models.py
class Property(models.Model):
 address = models.TextField()
 ...

class PropertyImage(models.Model):
 property = models.ForeignKey(Property, related_name='images')
 image = models.ImageField()
 is_front = models.BooleanField(default=False)

and:

# admin.py
class PropertyImageInline(admin.TabularInline):
 model = PropertyImage
 extra = 3

class PropertyAdmin(admin.ModelAdmin):
 inlines = [ PropertyImageInline, ]

admin.site.register(Property, PropertyAdmin)

The is front picture is boolean so I know which will be the picture to be shown on the announces

Problem

I don't know how to make validation so I can throw an eror If 0 or more that 1 picture were chosen as is_front can you please help me with the admin form validation?

Thank you!

One way you can do it is to create a clean method on PropertyImage which will be used to validate the data in the admin.

from django.core.exceptions import ValidationError

class PropertyImage(models.Model):
 property = models.ForeignKey(Property, related_name='images')
 image = models.ImageField()
 is_front = models.BooleanField(default=False)

 # Clean will only be called within the Admin.
 # If you have other places this needs to be verified,
 # you'll need to call it manually or move this logic into a ModelForm.
 def clean(self):
 images = self.property.images.all()
 # If we're editing, we want to exclude ourselves from the check.
 if self.id:
 images = images.exclude(id=self.id)
 if self.is_front and images.filter(is_front=True).exists():
 raise ValidationError("Only one image can have is_front set.")