On Tue, Jul 7, 2015 at 10:59 AM, Carlos Andre <[email protected]> wrote:
> example : I have two classes, respectively person contact.
> I want to contact class has , in its attributes , values worked coming from
> class person , such as name, pass in person , and size of the contact name
> in the class.
Ahh, what you probably want is a foreign key relationship from Contact
back to Person. See below.
I'm not sure what you mean by size, though. Is that a reference to the
qtdade field?
> I did something like this :
> from django.db import models
>
> class person ( models.Model ) :
> qtdade = models.IntegerField (default = 1 )
>
> class Meta :
> verbose_name_plural = ' Person '
>
> def valor_contato ( self):
> return self.qtdade * 2
>
> class contact ( models.Model ) :
> p = Person ()
> value = models.CharField ( max_length = 150, default = p.qtdade )
>
What you probably want is this:
class Contact( models.Model ) :
p = models.ForeignKey(Person, null=False)
Note that I used an uppercase letter to start your class (Contact).
Python classes in general use the CapWords naming convention. See PEP8
(https://www.python.org/dev/peps/pep-0008/#class-names).
This makes the Person attributes available via the Contact model
class, so you can do something like this:
a_person = Person.objects.create(qtdade=3)
a_contact = Contact.objects.create(p=a_person)
print(a_contact.p.qtdade)
##########
# Would print out 3
##########
Any attributes that are added to the Person class would then be
available to a Contact using the syntax I set above. See the
documentation on relationships between models:
https://docs.djangoproject.com/en/dev/topics/db/models/#many-to-one-relationships
As far as this line goes:
> value = models.CharField ( max_length = 150, default = p.qtdade )
It looks like you are trying to set a default in the model definition
that is dependent on a field in another model. Django doesn't support
this because this is a single value that is applied directly in the
database on the column during a migration/database initialization
(therefore, no objects exist in order to determine what that value
should be on a fresh migration). In general, you would set such a
value inside of the save() method for your model whenever a Contact is
saved, and use default='' (or default=None, but not recommended for
CharField fields) in the model definition above.
See this link for more information regarding the save() method on models:
https://docs.djangoproject.com/en/dev/topics/db/models/#overriding-predefined-model-methods
>
> 2015-07-07 4:08 GMT-03:00 James Schneider <[email protected]>:
>>
>> Can you give a simple example or analogy of what you are trying to do?
>>
>> -James
>>
>> On Jul 6, 2015 5:29 PM, "Carlos Andre" <[email protected]> wrote:
>>>
>>> Hello to all , I need to solve a problem. I have two classes of which
>>> have to use , in the second class, the first coming values. How to do this?
>>> Thanks for listening!
>>>
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