Deform/Colander validator that has access to all nodes?

Question

How do you define a custom validator in Deform/Colander that has access to all node values. I need to access the values from two fields in order to decide if a particular value

Answer 1

To place a validator for all colander fields we can simply do this

validator method:

def user_DoesExist(node,appstruct):
if DBSession.query(User).filter_by(username=appstruct['username']).count() > 0:
    raise colander.Invalid(node, 'Username already exist.!!')

Schema:

class UserSchema(CSRFSchema):
username = colander.SchemaNode(colander.String(), description="Extension of the user")
name = colander.SchemaNode(colander.String(), description='Full name')
extension = colander.SchemaNode(colander.String(),description='Extension')
pin = colander.SchemaNode(colander.String(), description='PIN')

View:

@view_config(route_name='add_user', permission='admin', renderer='add_user.mako')
def add_user(self):
    #Here you can provide validator method as a parameter. And you can validate any field you want.
    schema = UserSchema(validator = user_DoesExist).bind(request=self.request)
    form = deform.Form(schema, action=self.request.route_url('add_user'), buttons=('Add User','Cancel'))

Correct me if i am wrong in my scenario.

Thanks