Models and relationships

[Chris Strasser]

Hi ,I am fairly new to Django and am struggling with models hope someone can sort me out. 


Models:
class Organization(models.Model):  #customer or vendor person or company
    orgid = models.AutoField(db_column='OrgID', primary_key=True)  
    is_company = models.NullBooleanField(db_column='IsCompany', default =True)
    organizationname = models.CharField(db_column='OrgName', max_length=75,blank=True, null=True)
    main_phone = models.CharField(db_column='MainPhone',max_length=20, blank=True, null=True) 
...
...
 
class Location(models.Model):
    locationid = models.AutoField(db_column='LocationID', primary_key=True)  
    orgid = models.ForeignKey(Organization, db_column='OrgID')  
    locationname = models.CharField(db_column='LocationName', max_length=75, null=True)  
    address1 = models.CharField(db_column='Address1', max_length=200, blank=True, null=True)  
...
...

 class Contact(models.Model): 
    contactid = models.AutoField(db_column='ContactID', primary_key=True)  
    locationid = models.ForeignKey(Location, db_column='LocationID')  
    firstname = models.CharField(db_column='FirstName', max_length=50,blank=True, null=True)  
    lastname = models.CharField(db_column='LastName', max_length=50,blank=True, null=True) 
...
...

my problem is with reverse lookups (i think it is called) the docs say that i can access entries through blog.entry,(by lowercaseing the class)
it appears to me that i have the same setup with contact and location but i am getting errors ??


what I am trying to do is access a contacts address and organization at both the views level and the templates.(I would like to create a 
list of contacts, their company and their address ordered by contact name)

if someone would point me in the right direction it would be greatly appreciated. 

Thanks.

[Sadaf Noor]

If you have at least one entry in contact with a valid location, then it should work: 

from app.models import Contact
contact = Contact.all()[0]
print contact.locationid.locationname

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[Rafael E. Ferrero]

For start you don't need to specify the primary key (orgid for example) [1]

In foreingkeys you need to use related names [2]

In views use select_related() [3]

[1] https://docs.djangoproject.com/en/1.8/ref/models/fields/#primary-key
[2] https://docs.djangoproject.com/en/1.8/ref/models/fields/#foreignkey

[3] https://docs.djangoproject.com/en/1.8/ref/models/querysets/#select-related

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Rafael E. Ferrero

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[Chris Strasser]

I tried and this happens:

from main.models import Contact

>>> contact = Contact.all()[0]

Traceback (most recent call last):

  File "<console>", line 1, in <module>

AttributeError: type object 'Contact' has no attribute 'all'

>>> 

?? 

any ideas ?

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[Vijay Khemlani]

Try with

Contact.objects.all()[0]

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[Florian Schweikert]

On 06/07/15 14:04, Chris Strasser wrote:
> my problem is with reverse lookups (i think it is called) the docs say that i can access entries through blog.entry,(by lowercaseing the class)
> it appears to me that i have the same setup with contact and location but i am getting errors ??

I think you forgot about "_set".
Try something like:

Location.contact_set.all()

And please don't use AutoField, db_column and primary_key until you have
a good reason. Also ForeignKey fetches an object of the connected type,
not an id, so "contactid", ... is confusing ;)

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Florian

[Rafael E. Ferrero]

contacts = Contacts.objects.select_related()

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Rafael E. Ferrero

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[Chris Strasser]

WOO HOO !.. success ... thanks everyone...

 just needed a nudge in the right direction .... I will tackle the templates tomorrow and see where that takes me.

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[Rafael E. Ferrero]

Nice!! Chris good work !!

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