how to update another field on admin django - django

Question

models.py
Good night friends, I would like to know if there is a possibility that every time I register a new move, the django administrator checks what is a 'hydrographic region' and adds the value that is entering with the 'balance_box'.
class Movement(models.Model):
TYPE_MOVE = (
('1', 'Receita'),
('2', 'Despesa'),
)
regiao_hidrografica = models.ForeignKey(RegiaoHidrografica, verbose_name="Região Hidrografica", null=False)
origem = models.ForeignKey(Origem, verbose_name="Origem", null=False)
finalidade_recurso = models.ForeignKey(FinalidadeRecursos, verbose_name="Finalidade de Recursos", null=True)
descricao = models.TextField("Descrição", null=True)
valor = MoneyField(max_digits=10, decimal_places=2, default_currency='BRL')
data_refencia = MonthField("Data de Referencia", help_text="Informe mês e ano")
# data_refencia = models.DateField("Data de Referencia", null=True, blank=True, default=None)
tipo_movimento = models.CharField(max_length=1, default=1, choices=TYPE_MOVE)
def __str__(self):
return self.descricao
def update_total_valor(self):
total = 0
self.movimento_set:
total += mov.valor
self.saldo_caixa = total
self.save()
class RegiaoHidrografica(models.Model):
name = models.CharField("Nome", max_length=100, null=False)
sigla = models.CharField("Sigla", max_length=10, null=True)
taxa_inea = models.IntegerField(default=10, null=True)
taxa_trans = models.IntegerField(default=0, null=True)
saldo_caixa = MoneyField('Saldo em caixa estimado', max_digits=10, decimal_places=2, null=True, default=0, default_currency='BRL')
saldo_cc = MoneyField('Saldo em conta estimado', max_digits=10, decimal_places=2, null=True, default=0, default_currency='BRL')
def __str__(self):
return self.name
I tried something like this, create this method in the 'class MovimentoAdmin(admin.ModelAdmin)', but it did not work.
admin.py
def save_formset(self, request, form, formset, change):
instances = formset.save(commit=False)
for instance in instances:
instance.save()
formset.save_m2m()
instance.RegiaoHidrografica.update_total_valor()
Would anyone have a hint how I could do this?

Answer 1

Sounds to me like you need Django Signals.
You can register a listener on the post_save signal for your model Movement. The listener then would check for changes (it can also detect object creation with the parameter created) and react accordingly.
However, this would not only apply to Django Administrator but rather to all positions in your code where a Movement object got created. If you only create those objects via the admin site you are fine.
Otherwise, consider overwriting the Django ModelAdmin.save_model method:
Example in Django documentation. This method also provides you with the ability to detect object creation as well.
If you really want to use the save_formset method instead, check your code. update_total_valor is defined in and for class Movement and not RegiaoHidrografica according to your snippet, the method in admin.py is defined on Movement (which is fine, but then your access to RegiaoHidrografica looks wrong to me, since you are trying to access a class name instead of the model property).
I recommend to work with Django signals here, they provide a ton of comfort (but also have a trade-off: Added processing time when saving an object...