Here is an example:
Say you have
db.define_table('person',Field('name'))
db.person.name.requires=IS_IN_SET(build_set())
where build_set is computationally expensive. You only want to create the
set if you actually need the table. You can move it in the controller
action but does it belong there? Now you can do:
def set_requirements(person): person.name.requires=IS_IN_SET(build_set())
db.define_table('person',Field('name'),on_define=set_requirements)
Notice that this does not call build_set() until the table is actually
defined, moreover is does use the notation db.person and therefore does not
force table instantiation.
On Thursday, 23 August 2012 13:22:34 UTC-5, Anthony wrote:
>
> I'd also still be interested to see a real-world example of where this
>>> would be useful.
>>>
>>> Anthony
>>>
>>
>> Someone posted an example of GAE CPU Cycles, with class based Lazy Tables
>> it lower to half cycles. Also there is another user in the group which has
>> a huge traffic, so Lazy tables might be useful.
>>
>
> No, I meant an example of where the new on_delete argument would be useful.
>
> Anthony
>
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