I'm making a simple survey built around a modelform:
models.py
class Fruits(models.Model):
author = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
title = models.CharField(max_length=200, default='')
text = models.TextField(default='')
banana = models.BooleanField(default=False)
grape = models.BooleanField(default=False)
apple = models.BooleanField(default=False)
mango = models.BooleanField(default=False)
forms.py
class FruitPicker(ModelForm):
class Meta:
model = Fruits
fields = [
'title',
'text',
'banana',
'grape',
'apple',
'mango'
]
widgets = {
'text': forms.Textarea(attrs={"style": "height:10em;" "width:60em;"}),
'banana': forms.CheckboxInput(attrs={"style": "margin-left:350px;"}),
'grape': forms.CheckboxInput(attrs={"style": "margin-left:350px;"}),
'apple': forms.CheckboxInput(attrs={"style": "margin-left:350px;"}),
'mango': forms.CheckboxInput(attrs={"style": "margin-left:350px;"})
}
Now let's say I want to make sure the user has to select a minimum amount of 2 fruits, but a maximum amount of 3. How would I go about doing this on the back-end?
You can override the clean method of the form to check if between two and three BooleanFields are checked:
from django.core.exceptions import ValidationError
class FruitPicker(ModelForm):
# ⋮
def clean(self, *args, **kwargs):
data = super().clean(*args, **kwargs)
total = sum([data[x] for x in ['banana', 'grape', 'apple', 'mango']])
if not (2 <= total <= 3):
raise ValidationError('You should select between 2 and 3 fruits.')
return dataHere the sum(…) sums up the booleans and uses 0 for False, and 1 for True, it thus counts the number of Trues. If that number is not between 2 and 3, then it raises a ValidationError.