web2py: How to update form field value onvalidation

Question

I have a sample which looks quite like the one in the web2py-docs:

http://web2py.com/books/default/chapter/29/07/forms-and-validators#onvalidation

models/db.py:

db.define_table('numbers',
    # Field('user_id', 'reference auth_user'),
    Field('user_id', 'integer'),
    Field('b', 'boolean'),
    Field('c', 'integer')

# db.numbers.user_id.requires = IS_IN_DB(db, db.auth_user.id)
db.numbers.user_id.writable = db.numbers.user_id.readable = False
db.numbers.id.writable = db.numbers.id.readable = False

controllers/default.py:

def my_form_processing(form):
    if not form.vars.b:
       form.vars.c = None

# @auth.requires_login()   
def insert_numbers():
   # record = db(db.numbers.user_id==auth.user_id).select().first()
   record = db(db.numbers.user_id=1).select().first()
   db.numbers.c.show_if = (db.numbers.b == True)
   form = SQLFORM(db.numbers, record)
   if form.process(onvalidation=my_form_processing).accepted:
       session.flash = 'record inserted'
       redirect(URL())
   return dict(form=form)

but added some "magic":

In my original code the form requires you to be logged in and always loads the record with the user_id == auth_id. To simplify things the record for user_id==1 is always loaded.
If checkbox 'b' is not checked, hide field 'c' (see: Conditional fields)
If checkbox 'b' is not checked and the form is submitted, clear value 'c' (see: onvalidation)
FTR: if the record does not exist it will be INSERTed, if it already exists it will be UPDATEd. (web2py-magic).

This works quite well (the database-value of c is set to NULL if the 'b' is false) but here is the catch:

Check 'b' (field 'c' is shown) and enter a value in 'c' and submit the form. (b = True and c = $value in database) -> Fine.
The form is shown again with a checked 'b' and $value in 'c' -> Fine again.
Uncheck 'b' (field 'c' will get hidden) and submit the form. (b = False and c = Null in database (because of onvalidation=my_form_processing)) -> Fine too!
The form is shown again with an unchecked 'b' only but if you check 'b' again field 'c' has still $value in it (instead of an empty field).

How can I clear the form-value of field 'c'? (If I just reload the page while 'b' is False, 'c' will be an empty field. This problem only occurs on submit).

Can somebody help me with this?

After checking my sample code with my real code I just figured out that the _redirect(URL())_ line was missing all the time. Now it works. Thanks everyone! — dpat, Nov 19 '15 at 20:08

Boa · Answer 1 · 2015-11-19T22:26:43.303

0

If your goal is to simply conditionally delete that variable, one way to do it would be the following:

def insert_numbers():
   record = db(db.numbers.user_id=1).select().first()
   db.numbers.c.show_if = (db.numbers.b == True)
   form = SQLFORM(db.numbers, record)

   if form.validate(message_onsuccess = 'record inserted'):
       if not form.vars.b:
          del form.vars.c
       db['numbers'].insert(**form.vars)
       db.commit()   # just to be safe
       redirect( URL(...) )
   return dict(form=form)

edited Nov 19 '15 at 22:26

answered Nov 19 '15 at 16:47

Boa

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Hmm... After the change from _form.process()_ to _form.validate()_ (with _db[].insert_) the database is not getting updated. Did I miss something? – dpat Nov 19 '15 at 20:06
@dpat - Made some edits that should fix it. I'm guessing it was the 'next' param within 'validate()' that was screwing things up. – Boa Nov 19 '15 at 22:27

web2py: How to update form field value onvalidation

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