Problem in creating the perfect django custom validation

Question

I have this model for my accounting app:

class Simpleunits(models.Model):
    User       = models.ForeignKey(settings.AUTH_USER_MODEL,on_delete=models.CASCADE,null=True,blank=True)
    symbol     = models.CharField(max_length=32)
    formal     = models.CharField(max_length=32)

class Compoundunits(models.Model):
    User       = models.ForeignKey(settings.AUTH_USER_MODEL,on_delete=models.CASCADE,null=True,blank=True)
    firstunit  = models.ForeignKey(Simpleunits,on_delete=models.CASCADE)
    conversion = models.DecimalField(max_digits=19,decimal_places=2)
    secondunit = models.ForeignKey(Simpleunits,on_delete=models.CASCADE)

class Stockdata(models.Model):
    User        = models.ForeignKey(settings.AUTH_USER_MODEL,on_delete=models.CASCADE,null=True,blank=True)
    stock_name  = models.CharField(max_length=32)
    unitsimple  = models.ForeignKey(Simpleunits,on_delete=models.CASCADE,null=True,blank=True)
    unitcomplex = models.ForeignKey(Compoundunits,on_delete=models.CASCADE,null=True,blank=True)

I want to create a custom validation method under model class Stockdata that if the user mention both unitsimple and unitcomplex then they will get a validation error that "Only one unit should be given" and vice versa...

I mean to say that the user can only mention one unit either unitsimple or unitcomplex if they mention both then they will get a validation error...

Do anybody have any idea what should I do under def clean(self) function to accomplish this..???

Thank you in advance...

art · Accepted Answer · 2018-10-29 14:56:23Z

1

Create a model form for the create view of Stockdata and as you said, add a custom clean() method as given below.

class CreateStockData(forms.ModelForm):
   class Meta:
       model = Stockdata        
       fields= [....]
   ....
   def clean(self):
       cleaned_data = super(CreateStockData, self).clean()
       unitsimple = cleaned_data.get('unitsimple')
       unitcomplex = cleaned_data.get('unitcomplex')
       if unitsimple != None and unitcomplex != None:
           raise forms.ValidationError({'unitcomplex':["You are not supposed to select both values!"]})

Edit

In view of your comment, let me post the other way.

class Stockdata(models.Model):
    ....
    def clean(self):
        if self.unitsimple is not None and if self.unitcomplex is not None:
            raise ValidationError(
                {'unitcomplex':["You are not supposed to select both values!"]})
    def save(self, *args, **kwargs):
        self.full_clean()
        super().save(*args, **kwargs)

See Validating objects

edited Oct 29, 2018 at 14:56

answered Oct 27, 2018 at 11:25

art

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3 Comments

Niladry Kar Over a year ago

Yeah that can be done...But it is also possible in doing in model...I have done that...I only want to know the logic which you have provided...Thank you@art06

art Over a year ago

How do you display the error message to the form when you do it inside model?

Niladry Kar Over a year ago

I am connecting the model to the form under class meta and in template I have done this {{ form.non_field_errors }}...And that worked...The error message is showing in template and the user cannot submit the form...

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