Michael Bayer wrote:
> On Jan 24, 1:50 am, "chris e" <[EMAIL PROTECTED]> wrote:
>
>> I am planning on using sqlalchemy to build the api for a database I am
>> developing, and I was wondering if there is any type of column
>> verification that occurs before database commit.
>>
>> I.E.: a string column with length 40 would throw a verification
>> exception if a value longer that 40 characters was placed into it and
>> saved.
>>
>
> your database will throw an error. why reinvent the wheel ?
>
>
>> Additionally has anyone thought of implementing some sort of
>> verification support for objects that are mapped which would allow the
>> object to perform pre database action logic? The intent being that the
>> instance would check to see that the object meets additional business
>> logic requirements before it is inserted or updated.
>>
>> I.E.: a User business object would verify that the userid was part of
>> the [a-z] [A-Z]and [0-9] character classes, and if not an exception
>> would be raised to prevent the database action.
>>
>
> thats exactly the kind of thing you should write into your
> application. has nothing to do with an ORM. for generic validation
> widgets to help, check out formencode ( http://formencode.org/ ).
>
>
>
(Just to share a method which woks well for me :)
What I usually to perform validation is to create a property()
(_set_attribute(), _get_attribute()) for each mapped column, then I use
the column_prefix="_" attribute in SQLAlchemy.
After that I have a function which iterate on the columns
(YourMappedObject.c.keys()) and use a try / except with a setattr (it's
a bit more sophisticated than that in fact), for example :
assign_mapper(session_context, Language, table_languages, column_prefix='_')
class Language(object):
def _set_iso_code(self, value):
try:
value = ''.join(value.split()).lower()
except AttributeError:
raise Invalid('iso code must be a string')
if len(value) == 2:
self._iso_code = value
else:
raise Invalid('Invalid iso code')
def _get_iso_code(self):
return self._iso_code
iso_code = property(_get_iso_code, _set_iso_code)
(...)
then I do something like (not complete):
def populate(MappedObject, values):
errors = []
for c in MappedObject.c.keys():
value = values.get(c, Undefined())
if value is not Undefined:
try:
setattr(MappedObject, c , value)
except Invalid, e:
errors.append(str(e))
return errors
also, I have in my models a __before_save__ / __before_update__ which
check additional things like NOT NULL constraints (!None), ...
> >
>
--
Julien Cigar
Belgian Biodiversity Platform
http://www.biodiversity.be
Université Libre de Bruxelles
Campus de la Plaine CP 257
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Boulevard du Triomphe, entrée ULB 2
B-1050 Bruxelles
office: [EMAIL PROTECTED]
home: [EMAIL PROTECTED]
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