calling a function to obtain a model field value - django

Question

I'm trying to get a unique value for a field (unique within the db column).
my code (other model fields omitted):
class PlatformUserChildren(models.Model):
dashboard = models.CharField('dashboard URL', max_length=64, unique=True, default=createDashboardCode(self))
def createDashboardCode(self):
stringCheck = False
while stringCheck is False:
newString = str(uuid.uuid4())[:32]
doesStringExist = newString in self.dashboard
if not doesStringExist:
stringCheck = True
return newString
I'm getting name 'self' is not defined as an error.
What should I be passing to the function so that I can check the db column to ensure the value is unique -or- is there a built-in way of doing this?
What I've already tried or looked at:
setting unique=True for the field and using default=uuid.uuid4 - that gives me duplicate values and generates a validation error (SO link)
I'm aware of Django 1.8's UUID field, however i'm on 1.7

Answer 1

The problem lies in the following line (indented for better readability) as you already know and mentioned before:
dashboard = models.CharField(
'dashboard URL',
max_length=64,
unique=True,
default=createDashboardCode(self)
)
In this part:
default=createDashboardCode(self)
you're calling the method createDashboardCode with the argument self. This is wrong, because you never pass self to a method as it is passed by Python. Whenever you call the method createDashboardCode you should do it this way:
createDashboardCode()
That's it, you're not passing the argument self explicitly.
You're getting an error "name 'self' is not defined" because self is not defined. There is no variable self in your code that you can pass to the method.
Now we're one step further, but your problem won't be solved if you just apply this slight change to your code.
The return value from the method createDashboardCode will be assigned to default. That's not what you really want. You have to assign a reference of the method to default:
default = createDashboardCode
Pay attention to the missing brackets. This will call the method every time a new instance of the model is created
Define a function:
def my_function():
print "hello"
and run it in the Python interpreter:
# once like this
my_function()
# and again like this
my_function
and you'll see the difference. That should help you to better comprehend this issue.