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django access many to many m2m field value before saving

notorious answered on August 3, 2022 Popularity 2/10 Helpfulness 1/10

answer django access many to many m2m field value before saving

django access many to many m2m field value before saving

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# for M2M fields override clean() method of forms.ModelForm
# (instead of clean() method of models.Model) to get access
# to both already saved and updated values

class DjangoModelForm(forms.ModelForm):
    class Meta:
        model = DjangoModel
        fields = ('field1', 'field2', 'field3')

    def clean(self):
        super(DjangoModelForm, self).clean()

        field1_saved = None
        field1_updated = self.cleaned_data.get('field1')

		if self.instance.pk:
        	# already saved instance
        	field1_saved = self.instance.field1
            
        	if field1_saved != field1_updated:
        		raise forms.ValidationError("Custom error message")

        return self.cleaned_data
      
@admin.register(DjangoModel)
class DjangoModelAdmin(admin.ModelAdmin):
    form = DjangoModelForm
    list_display = (
        "id", "field1", "field2", "field3"
    )

Popularity 2/10 Helpfulness 1/10 Language python

Source: Grepper

Tags: django field m2m many-to-many python

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Contributed on Aug 03 2022

notorious

0 Answers Avg Quality 2/10

django access many to many m2m field value before saving

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