Compute insert-only

[Louis Amon]

I'm trying to hard-code URLs for SEO purposes so I have a function ("make_url(row)") that builds the paths based on other fields.

I was thinking of using "compute=make_url", but it seems that update operations also call the compute.

Is there a way to use compute only on INSERT operations, and not on UPDATE ?

[Niphlod]

code an _after_insert callback.

[Louis Amon]

That’d do the trick nicely.

Thanks Niphlod!

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[Anthony]

Might be easier with a _before_insert callback, so you can add the new value along with the initial insert instead of after:

db.mytable._before_insert.append(lambda fields: fields.update(url=make_url(fields)))

Anthony

[Louis Amon]

My url builder requires the « id » field so _before_insert wouldn’t work.

That’s a good suggestion though!

Thanks Anthony :)

[Anthony]

Got it. In that case, compute wouldn't have worked anyway.

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[黄祥]

compute field not work when using after insert callback too.

e.g. 

def __after_insert_delivery_order(f, id):

db(db.customer.id == f.customer).update(last_delivery_order_net = f.gross - f.tarra) # work

#db(db.customer.id == f.customer).update(last_delivery_order_net = f.net) # not work

def on_define_delivery_order(table): 

table._after_insert.append(__after_insert_delivery_order)

table.net.compute = lambda r: r['gross'] - r['tarra']

db.define_table('delivery_order', 

Field('delivery_order_no'), 

Field('customer', 'reference customer'), 

Field('tarra', 'integer'),

Field('gross', 'integer'),

Field('net', 'integer'),

on_define = on_define_delivery_order, 

format = '%(delivery_order_no)s')

not sure is it bug, or normal behaviour.

best regards,

stifan

[Massimo Di Pierro]

I see the problem, the computed field is computed by the insert function while f in the _after_insert_delivery_order are the record parameters as passed to the insert function (before the field is computed). So I'd say this is not supposed to work. Open a ticket with your code and we will consider the improvement.

[黄祥]

done

https://github.com/web2py/web2py/issues/1101

thanks and best regards,

stifan