Change a field of the parent class in the Django models

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Change a field of the parent class in the Django models

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I have a parent class where I have an attribute that I want to modify according to the child class:

class Service(models.Model):
   # otros atributos
   SERVICE_TYPE = {
       'None': 'Unknown service type',
       'visa': 'Visa',
   }
   service_type = None

   def get_service_type(self):
       if self.service_type:
           return self.service_type
       else:
           return self.SERVICE_TYPE['None']

And I have several classes that inherit from this, one of them is the following:

class Visa(Service):
    # atributos de esta clase

The problem is that when I create an object of type Visa the attribute service_type of the parent class Service is never modified (it is always None). I have tried to modify the method save of Model and also modify it directly in the view to create and it does not work.

modifying the `save` method:

class Visa(Service):
    # atributes
    def save(self, force_insert=False, force_update=False, using=None, update_fields=None):
    self.service_type = 'visa'
    return super(Visa, self).save(force_insert, force_update, using, update_fields)

modifying the attribute in the view:

class ServiceCreateView(generic.CreateView):
    def form_valid(self, form):
        self.object = form.save(commit=False)
        self.object.service_type = 'visa'
        return super(ServiceCreateView, self).form_valid(form)

python python-3.x django django-models

asked by Reinier Hernández Ávila 09.11.2018 в 20:53

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1 answer

Null Pointer Exception, because when sending values to the parent class Encryption, then the child classes do not receive them to perform the methods Odoo, show records for common class

score 0 · Accepted Answer

Reading the Django documentation on Model inheritance I found a way to be able to access the value of the parent class. This is how the models would look:

models.py

class Service(models.Model):
    # otros atributos
    SERVICE_TYPE = {
        'None': 'Tipo de servicio desconocido',
        'visa': 'Visado',
        'passport': 'Pasaporte',
    }
    service_type = None

    def get_service_type(self):
        if self.service_type:
            return self.SERVICE_TYPE[self.service_type]
        else:
            return self.SERVICE_TYPE['None']

class Visa(Service):
    # atributos de la clase Visa
    service_type = 'visa'

class Passport(Service):
    # atributos de la clase Passport
    service_type = 'passport'

Then the template would look like this:

templates / index.html

{% if service.visa %}
    {{ service.visa.get_service_type }}
{% elif service.passport %}
    {{ service.passport.get_service_type }}
{% else %}
    {{ service.get_service_type }}
{% endif %}

Showing Visa if the object is of the class Visa or shows Passport if it is an instance of the class Passport . If you do not belong to any of these classes, then it shows Unknown service type .

Change a field of the parent class in the Django models

modifying the save method:

modifying the attribute in the view:

1 answer

models.py

templates / index.html

modifying the `save` method: