ForeignKey django 1.1.1 model

I have

class staff_name(models.Model):

    firstname = models.CharField(max_length=150)
    surname = models.CharField(max_length=150)



class inventory_transaction(models.Model):

    staffs = models.ForeignKey(staff_name)

I want to get or create staff surname and first name through inventory_transaction

I used these code below

inventory_transaction.objects.get_or_create(staffs__surname__contains=sname,staffs__firstname__c开发者_如何学JAVAontains=fname) 

I got this error "staffs__surname__contains can not be defined"

What have i done wrong ?

thanks

Hmm based on the documentation of get_or_create():

In English, that means start with any non-'defaults' keyword argument that doesn't contain a double underscore (which would indicate a non-exact lookup).

I would say what you want to do is not possible as your query could return more than one result. The arguments passed to get_or_create() must be in a way that a unique result is returned.

You could try __exact instead of __contains:

inventory_transaction.objects.get_or_create(staffs__surname__exact=sname,staffs__firstname__exact=fname) 

But I don't think that get_or_create() can create foreign key objects automatically.

So probably the easiest thing in this case is this:

try:
    itrans = inventory_transaction.objects.get(staffs__surname__contains=sname,staffs__firstname__contains=fname)
except inventory_transaction.DoesNotExist:
    staff = staff_name(firstname=fname, surname=sname)
    staff.save()
    itrans = inventory_transaction(staffs=staff)
    itrans.save()

Btw common practice is to use capital names for classes and I wouldn't use underscores as they are also used in DB lookups. That said, rename your classes to StaffName and InventoryTransaction