Anthony,
The _before_insert works perfectly. Thank you.
Andrew
On Sun, Jul 10, 2016 at 9:53 PM, Anthony <abasta...@gmail.com> wrote:
> Here's a potentially better option that will work even in appadmin and
> doesn't require an extra callback if you need to do an insert followed by an
> update in the same request:
>
> db.define_table('mytable',
> Field('modifiable_number', 'integer', requires=IS_NOT_EMPTY()),
> Field('original', 'integer', readable=False, writable=False))
>
> db.mytable._before_insert = [lambda fields:
> fields.update(original=fields.get('modifiable_number'))]
>
> With the above solution, there is no default or compute attribute. Instead,
> before an insert (but not before an update), the value of the "original"
> field is set to match the value of the "modifiable_number" field.
>
> Anthony
>
>
> On Sunday, July 10, 2016 at 11:43:22 PM UTC-4, Anthony wrote:
>>
>> On Sunday, July 10, 2016 at 4:38:33 PM UTC-4, ahz...@gmail.com wrote:
>>>
>>> In my application a user enters a boolean value, and later the user can
>>> modify the value. I want to save the original value in another field, and
>>> the user shouldn't be able to see or alter the original value.
>>>
>>> Based on the stackoverflow conversation I tried a simple table with two
>>> methods
>>> db.define_table('mytable',
>>> Field('start_number', 'integer', requires=IS_NOT_EMPTY()),
>>> Field('n1', 'integer', default=request.post_vars.start_number),
>>
>>
>> n1 won't work because it is writable and therefore appears in the form,
>> which means even if you leave it blank, an empty string is submitted as its
>> value, which SQLFORM converts to a 0 (the default value is inserted only if
>> no value is submitted).
>>
>> Here are two options:
>>
>> db.define_table('mytable',
>> Field('modifiable_number', 'integer', requires=IS_NOT_EMPTY()),
>> Field('original1', 'integer', readable=False, writable=False,
>> default=request.post_vars.modifiable_number),
>> Field('original2', 'integer', readable=False, writable=False,
>> compute=lambda r: r.modifiable_number))
>>
>> db.mytable._before_update = [lambda t, f: setattr(db.mytable.original2,
>> 'compute', None)]
>>
>> Because original1 is not writable, it will not appear in the form, which
>> means no value will be submitted for it and therefore its default value will
>> be inserted. Note, however, that this will not work in appadmin, which
>> ignores the "writable" attribute and will therefore include original1 in the
>> insert form.
>>
>> original2 will use the computed value only on the initial insert. The
>> _before_update callback removes the "compute" attribute before any updates,
>> so no new value will be computed on updates. Note, if you need to do an
>> insert after an update during the same HTTP request (which is probably not a
>> common scenario), you would also need to add an _after_update callback to
>> restore the "compute" attribute after the update.
>>
>> Anthony
>
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