On Dec 23, 8:11 pm, "dick...@gmail.com" <dick...@gmail.com> wrote:
> i'm working on a simple concept i'm sure others have solved, but i
> can't get it.
>
> basically, given some <xml> input, i parse it, find which objects to
> create, and do it.
>
> so with a model:
>
> class Foo(models.Model):
> name = models.CharField(max_length=20)
>
> and input xml of <request><Foo><name>bar</name></Foo></request>
>
> my view would parse that xml, find the Element Request name "Foo",
> instantiate Foo, set the "name" value to bar, and save it.
>
> import myproject.test.models as test_models
> createobj = getattr(test_models, "Foo")
> setattr(createobj, "name", "bar")
> createobj.save()
>
> the current code there above gives me
>
> unbound method save() must be called with Foo instance as first
> argument (got nothing instead)
>
> i've also tried
> save = getattr(createobj, "save")
> save(createobj)
>
> unbound method save() must be called with Foo instance as first
> argument (got ModelBase instance instead)
>
> i've probably gone about the whole problem all wrong, so feel feel to
> correct this approach if it is way off base
I wouldn't say you were way off base, but you haven't quite grasped
the Python object model, nor what Django does specifically to model
classes.
By going getattr(test_models, 'Foo') you're simply getting the model
class, not instantiating it. In Python, classes themselves are first-
class objects, and you can pass them around and set attributes on them
just like any object. So using setattr to set a 'name' property on the
object does nothing more than give the class object a value for name.
So the missing step is instantiation - and you can do this with your
dynamic class variable just like any other class name, by simply
calling it.
obj_class = getattr(test_models, "Foo")
createobj = obj_class()
setattr(createobj, "name", "bar")
createobj.save()
However, having said all this, there is a much easier way using some
Django helper models.
from django.db.loader import get_model
obj_class=get_model('test', 'Foo')
values = {'name':'bar'}
createobj = obj_class.objects.create(**values)
The last line here is using the create method, which instantiates and
saves an object all in one. It also uses the fact that Python allows
you to use a dictionary to pass in keyword arguments - eg name='bar' -
and of course dictionary keys can be strings, so could be loaded
directly from your XML.
Hope that helps,
--
DR.
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