On May 7, 2007, at 2:31 PM, Cory Johns wrote:
>
> I'm creating a general routine that is intended to take an
> arbitrary dict of
> attribute / value pairs and an ORM object instance, and use the
> dict to
> update the properties of the ORM instance, without knowing a priori
> whether
> the attributes might be relations to other tables. The problem I
> ran in to
> is when a property that is a relation needs to be created anew,
> because then
> I don't know what class to create an instance of. From looking at the
> source, I found what I was looking for under the argument attribute
> of the
> PropertyLoader class, so I am currently doing along the lines of:
>
> attr_class = object_mapper(ormvar).properties[attr].argument
> new_instance = attr_class()
> setattr(ormvar, attr, new_instance)
>
> However, this feels like it might be a bit fragile, as the argument
> attribute isn't explicitly document that I could find. Is there an
> API /
> documented way of determining the class that represents a particular
> attribute, as determined by mapper() or relation()?
a better choice would be property.mapper.class_ , i.e.
object_mapper(ormvar).properties[attr].mapper.class_
but not every entry inside of 'properties' is a PropertyLoader,
theres also column- and synonym- based properties (and someday may be
others).
i would think that a dict-based method of updating object attributes
would itself be "shaped" the same way as an object graph, and you
wouldnt have to know about classes/attribute types explicitly ? i.e.
{
'attr1': 'somevalue',
'attr2': {
'subattr1':'somevalue'
}
}
i.e. the fact that "attr2" points to a dict means that its an object-
holding attribute, with its own attributes.
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