[FE-discuss] Compound validators usage

[Michael Jenny]

Hi there,

i have a schema validator and want to use another compound validator
(SimpleFormValidator) from within the schema.

E.g. I do something along the lines:


def validate_text(value_dict, state, validator):

# validation of text_field goes here. check value_dict for
bool_field's value to determine what to do next.


class ProductConfigurationSchema(Schema):
filter_extra_fields = True
allow_extra_fields = True

bool_field = validators.Bool()
text_field = SimpleFormValidator(validate_text)


This does not work as the schema does not expect that its fields are
compound validators. It doesn't pass the value_dict to the
SimpleFormValidator but rather a single value. This results in the
following errror in SimpleFormValidators to_python method:

value_dict = value_dict.copy()
AttributeError: 'unicode' object has no attribute 'copy'


I followed that route because I want to achieve the following:

The visibility of the text_field depends on the bool_field. Therefore I'd
thought I write a custom method that checks the state of the bool when
validating the text_field. If it is set, I would perform the actual
validation. If the bool is not set, the text_field is irrelevant and
validating would essentially be a no-op.


Any tip how to tackle this?


Cheers, prinz.

[Chris Lambacher]

Generally want SimpleFormValidators to be either pre_validators or
chained_validators see the docs here:
http://www.formencode.org/en/latest/Validator.html#compound-validators

So I would normally do:

class ProductConfigurationSchema(Schema):
filter_extra_fields = True
allow_extra_fields = True

bool_field = validators.Bool()
text_field = UnicodeString(max=100)

chained_validators = [ SimpleFormValidator(validate_text) ]

In this case, the main validator gets the bare minimum validation (I must
be a unicode string and may have a max length of 100). Following on that
you do form level validation in the chained_validators so I would expect
validate_text do do something like make text_field required if bool_field
is true (Note that there is a good model for building that built in a
RequireIfMissing/RequireIfPresent
http://www.formencode.org/en/latest/modules/validators.html#formencode.validators.RequireIfMissing
).

One thing you can do with pre_validtors is throw data away if a value is
set. So if your Bool() field was for deletion, you could remove the other
data from the form so that incorrect data does not cause a validation error.

-Chris

Post by Michael Jenny
Hi there,
i have a schema validator and want to use another compound validator
(SimpleFormValidator) from within the schema.
# validation of text_field goes here. check value_dict for
bool_field's value to determine what to do next.
filter_extra_fields = True
allow_extra_fields = True
bool_field = validators.Bool()
text_field = SimpleFormValidator(validate_text)
This does not work as the schema does not expect that its fields are
compound validators. It doesn't pass the value_dict to the
SimpleFormValidator but rather a single value. This results in the
value_dict = value_dict.copy()
AttributeError: 'unicode' object has no attribute 'copy'
The visibility of the text_field depends on the bool_field. Therefore I'd
thought I write a custom method that checks the state of the bool when
validating the text_field. If it is set, I would perform the actual
validation. If the bool is not set, the text_field is irrelevant and
validating would essentially be a no-op.
Any tip how to tackle this?
Cheers, prinz.
------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and
threat landscape has changed and how IT managers can respond. Discussions
will include endpoint security, mobile security and the latest in malware
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
_______________________________________________
FormEncode-discuss mailing list
https://lists.sourceforge.net/lists/listinfo/formencode-discuss