CODEWITHSUNDEEP
pythondjango
kosta5
kosta5

Reputation: 1138

django model.delete() raises ValueError - needs to have a value for field before this many-to-many relationship can be used

I have a overritten save_model() method in my django ModelAdmin class. This model has a ManyToMany field. My save_model looks like this:

def save_model(self, request, obj, form, change):
        creating = False
        to_delete = False
        if not obj.pk:
            creating = True
        obj.save()
        form.save_m2m()
        # DETECT SOMETHING (some complicated conditions) HERE ...
        detected =True
        if detected:
           obj.delete() # --> here is my problem

Traceback:
File "/Library/Python/2.7/site-packages/django/core/handlers/base.py" in get_response
  111.                         response = callback(request, *callback_args, **callback_kwargs)
File "/Library/Python/2.7/site-packages/django/contrib/admin/options.py" in wrapper
  366.                 return self.admin_site.admin_view(view)(*args, **kwargs)
File "/Library/Python/2.7/site-packages/django/utils/decorators.py" in _wrapped_view
  91.                     response = view_func(request, *args, **kwargs)
File "/Library/Python/2.7/site-packages/django/views/decorators/cache.py" in _wrapped_view_func
  89.         response = view_func(request, *args, **kwargs)
File "/Library/Python/2.7/site-packages/django/contrib/admin/sites.py" in inner
  196.             return view(request, *args, **kwargs)
File "/Library/Python/2.7/site-packages/django/utils/decorators.py" in _wrapper
  25.             return bound_func(*args, **kwargs)
File "/Library/Python/2.7/site-packages/django/utils/decorators.py" in _wrapped_view
  91.                     response = view_func(request, *args, **kwargs)
File "/Library/Python/2.7/site-packages/django/utils/decorators.py" in bound_func
  21.                 return func(self, *args2, **kwargs2)
File "/Library/Python/2.7/site-packages/django/db/transaction.py" in inner
  209.                 return func(*args, **kwargs)
File "/Library/Python/2.7/site-packages/django/contrib/admin/options.py" in add_view
  956.                 self.save_related(request, form, formsets, False)
File "/Library/Python/2.7/site-packages/django/contrib/admin/options.py" in save_related
  731.         form.save_m2m()
File "/Library/Python/2.7/site-packages/django/forms/models.py" in save_m2m
  83.                 f.save_form_data(instance, cleaned_data[f.name])
File "/Library/Python/2.7/site-packages/django/db/models/fields/related.py" in save_form_data
  1273.         setattr(instance, self.attname, data)
File "/Library/Python/2.7/site-packages/django/db/models/fields/related.py" in __set__
  859.         manager = self.__get__(instance)
File "/Library/Python/2.7/site-packages/django/db/models/fields/related.py" in __get__
  846.             through=self.field.rel.through,
File "/Library/Python/2.7/site-packages/django/db/models/fields/related.py" in __init__
  538.                                  (instance, source_field_name))

Exception Type: ValueError at /admin/lawis_core/invoice/add/
Exception Value: "<Invoice: 1301000>" needs to have a value for field "invoice" before this many-to-many relationship can be used.

Upvotes: 0

Views: 576

Answers (1)

Dirk Eschler
Dirk Eschler

Reputation: 2569

Could it be that just forgot to call the super class? Like this:

class YourAdmin(admin.ModelAdmin)
    def save_model(self, request, obj, form, change):
        super(YourAdmin, self).save_model(request, obj, form, change)  
        # Your code ...

Upvotes: 1

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