Re: eval if an object meets with a queryset.

On Tue, Mar 1, 2011 at 2:07 PM, Marc Aymerich <glicerinu@gmail.com> wrote:
> On Tue, Mar 1, 2011 at 1:46 PM, Masklinn <masklinn@masklinn.net> wrote:
>> On 2011-03-01, at 13:18 , Marc Aymerich wrote:
>>>
>>> Hi Masklinn, I never use jquey's :(
>> Not a problem. The .is method simply takes a CSS selector and returns a boolean flag indicating whether the selected object(s) match the selector: $('a').is('a') is trivially going to return `true` for instance.
>>
>>> My idea is that the end user can define their own arbitrary expression
>>> in order to match a subset of objects from a particular class. For
>>> example this is the class that handle the expression.
>>>
>>> class Service(models.Model):
>>>    content_type = models.ForeignKey(ContentType)
>>>    expression = models.CharField(max_length=255)
>>>    price = models.PositiveIntegerField()
>>>
>>> So, with this class the admin of my application can say: Active .ORG
>>> domains costs 10€ , active .ES and .NET domains costs 25€ …
>> But for that you should be able to use regular filters no? Build the right filtering kwargs (or a series of Q objects if you need arbitrary complexity, probably) from the stuff provided by the user and then call `filter` with that, and you should get the correct result shouldn't you?
>>
>
> Hi,
> what I want is a method for Service class that, given an object,
> return their price. As far as I know I can't evaluate a queryset
> against an object. Isn't it?
>

Summarizing, I want to be able of:

#Given a Domain instance
domain = Domain.objects.get(pk=2)
#Get their price
price = Service.get_price(domain)

class Domain(models.Model):
active = models.BooleanField()
root = models.CharField(max_length=6)

class Service(models.Model):
content_type = models.ForeignKey(ContentType)
expression = models.CharField(max_length=255)
price = models.PositiveIntegerField()

@classmethod
def get_price(cls, obj):
ct = ContentType.objects.get_for_model(obj)
for service in cls.objects.filter(content_type=ct):
if service._expression_match(obj): return service.price

def _expression_match(obj):
""" This method evaluates the expression against obj """

I'm wondering what is the best way to implement _expression_match method :)

thanks!

--
Marc

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