See
http://web2py.com/books/default/chapter/29/06/the-database-abstraction-layer#on_define.
On Thursday, March 17, 2016 at 6:13:35 PM UTC-4, Lisandro wrote:
>
> I will bother with one last related question: *what about callback
> triggers?*
> I'm defining them like this:
>
> db.define_table('mytable', Field('field1'), Field('field2')) # defines
> the table
> from myglobals import myfunction # imports global function
> db.mytable._after_update.append(lambda s, r: myfunction(s, r)) # defines
> after update callback trigger
>
> In this case, I guess lazy_tables=True wouldn't make sense, because I'm
> calling db.mytable so it triggers the definition of the table.
>
> Is there a way of specifying callback triggers directly when calling
> define_table?
>
>
>
>
> El jueves, 17 de marzo de 2016, 15:27:22 (UTC-3), Lisandro escribió:
>>
>> Oh I see! So I can define the virtual/method fields that way, and then it
>> does make sense to keep using lazy_tables. Completely missed that point.
>>
>> Thank you very much!
>> As always, web2py's community rocks.
>>
>>
>>
>> El jueves, 17 de marzo de 2016, 14:59:35 (UTC-3), Anthony escribió:
>>>
>>> On Thursday, March 17, 2016 at 1:53:43 PM UTC-4, Lisandro wrote:
>>>>
>>>> Thank you very much for the quick answer.
>>>>
>>>> Your first comment made me think about the "lazy_tables" with the
>>>> definition of virtual method fields.
>>>> If you say that doing db.tablename the table is no longer lazy, *then
>>>> it wouldn't make sense to use lazy_tables in a particular case where
>>>> almost
>>>> each table has a virtual method field, am I right?*
>>>>
>>>> I mean, for example, if this is my model:
>>>>
>>>> db.define_table('first_table', Field('field1'), Field('field2'))
>>>>
>>>> db.first_table.field3 = Field.Method(lambda row: 'value for field3')
>>>>
>>>
>>> This won't help with db.auth_user, which is defined automatically
>>> (though you can define it manually yourself if preferred), but you can
>>> simply do:
>>>
>>> db.define_table('first_table',
>>> Field('field1'),
>>> Field('field2'),
>>> Field.Method('Field3', lambda row: 'value for field3'))
>>>
>>> Note, the first argument of Field.Method() and Field.Virtual() should
>>> always be the field name anyway, even if you are defining them like this:
>>>
>>> db.mytable.myfield = Field.Method('myfield', ...)
>>>
>>> There are particular cases where leaving the name out can lead to
>>> problems.
>>>
>>> Anthony
>>>
>>
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