Question

I have model with ManyToManyField field. I also have ModelForm that uses this model.

How to define error_messages for such field?

Example:

class Article(models.Model):
    categories = models.ManyToManyField(Category)

class ArticleForm(ModelForm):
    class Meta(ContentForm.Meta):
        model = Article

I want to override ‘required’ error message for categories field in ArticleForm model.

I was Googling about this problem but all solutions not work either they are not form ModelForm or for ManyToManyField.

Answer 1

You could try to do your own validation for this field. In model set for m2m field blank=True, and in form implement clean_categories method. If field categories is not valid, raise exception with your content.

In model:

categories = models.ManyToManyField(Category, blank=True)

In form:

def clean_categories(self):
    if not self.cleaned_data.get('categories'):
        raise forms.ValidationError('My custom message')
    return self.cleaned_data['categories']