I've been working for a while on a very flexible (and so increasingly 
complex) multiple-select widget that can be re-populated from the db via 
ajax (without submitting the form). One think I had to do was figure out 
how to get the name of the table referenced by the field using my widget. 
With some help from the folks here I found this solution:

    referencetable = myfield.requires[0].ktable

I'm starting to realize, though, that this is fragile. I know it's doing an 
end-run around the DAL api (accessing implementation details instead of the 
stable api). I also found recently that this was broken by the IS_EMPTY_OR 
validator. For the moment I'm hacking a  solution by doing this:

    try:
        referencetable = myfield.requires[0].ktable
    except AttributeError:  
        # because IS_EMPTY_OR doesn't have a property .ktable, 
        # it's on the second, wrapped validator
        referencetable = myfield.requires[0].other.ktable

But I'm digging myself a deeper hole. Now I'm using a second implementation 
detail (the "other" instance variable of IS_EMPTY_OR) and my widget is that 
much more prone to being broken by future releases.

So I'm wondering whether 

(a) there's a way to access this data via the api that I'm just missing; or 
(b) this is reason to add access to the referenced table to the api.

This could be as simple as adding a get_reference_table() method to the 
validators that (for the time being) draws on the instance variables I've 
been using. 

    # in IS_EMPTY_OR
    def get_reference_table(self):
        return self.other.ktable

    # in IS_IN_DB
    def get_reference_table(self):
        return self.ktable

I'm not sure, though, whether the validator is the best place for that 
method. Should it be a method of Field instead? (That is, if others see a 
need for this at all.)

Cheers,

Ian

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