I figured out how to open a ticket, and what to put into it. I provided a diff file against the source in trunk to add my feature. It does not affect current users but only adds the ability to map "None" into a different value for Fields.
code.google.com/p/web2py/issues/detail?id=1183 -- Joe B. On Monday, November 5, 2012 8:45:22 PM UTC-8, Massimo Di Pierro wrote: > > please open a ticket about this. I will take care of it asap. > > On Thursday, 1 November 2012 15:54:53 UTC-5, Joe Barnhart wrote: >> >> This proposal solves a problem I have when formatting Field values. I >> created a custom Validator class which maps the value None into a string >> (such as "N/A" or "NT"), but the mapping was ignored because the current >> Field processing provides an early exit if the value of the Field is None, >> i.e. it never reaches the Validator object for formatting. >> >> Proposal: >> >> I propose creating a new keyword variable for Field objects, called >> "map_none" which is initialized to None for backwards compatibility: >> >> >> map_none = None, >> >> . . . >> >> self.map_none = map_none >> >> >> >> Next, we use the value of map_none as the return value for None from the >> formatter function: >> >> >> def formatter(self, value): >> requires = self.requires >> if value is None or not self.requires: >> return value or self.map_none >> >> >> Last, for symmetry, we alter the validator to replace any occurrence of >> map_none with None when processing items to go back into the database. In >> my case it will accept any entered value of "NT" and map it back into None >> when storing row data in the database. I would also use it to replace >> empty strings with None (which I prefer over empty strings in the database >> when values are not entered). >> >> >> def validate(self, value): >> if not self.requires: >> return ((value if value!=self.map_none else None), None) >> requires = self.requires >> if not isinstance(requires, (list, tuple)): >> requires = [requires] >> for validator in requires: >> (value, error) = validator(value) >> if error: >> return (value, error) >> return ((value if value!=self.map_none else None), None) >> >> This approach allows any mapping of None into an object of the user's >> choosing, and provides the mapping in a consistent and bi-directional >> manner. It preserves all existing behavior of Validators. The only cost >> is an additional variable carried in Field objects and the time expended on >> the trivial "if" tests to map the value. >> >> Any thoughts? >> >> -- Joe B. > > --
