2017-12-29 7:31 GMT-03:00 Cato Nano <[email protected]>:
> Hello,
Hello
>
> Could anyone give me a brief, clear example of how to have a calculated
field ?
>
> I' m trying to have my first calculated field
>
> I have 2 Date fields and I want my calculated field to be the difference
in days between the 2 dates
>
> How do I set that ?
You are looking for fields.Function [1]
Here's an example which returns an Integer [2] check for the
'on_change_with_currency_digits' method in it [3]
(This is an on_change_with*, not an on_change*)
>
> The documentation says that "on_change" is an attribute of the filed,
like this
>
> Field.on_change
>
> Does this mean that I should write this ?
> fields.Numeric('duration', digits=(2,), on_change=someDatefield) ?
>
> Can I trust the documentation on this ?
The documentation is correct, but as your interpretation may be wrong, the
best way to finish to understand the docs is usually to look for examples
in the code.
>
> In the code of the sale.sale model, on_change is not used like that, but
it' s quite complicated and I' ma bit overwhelmed
on_change* methods are usually used as the doc says, to update the value of
other fields when the one you want changes.
For example on_change_foo() will run each time the field foo changes, and
so allow you to update another field 'bar'. in this case you have to add
'bar' (or any other field value you may need for the computation) in the
depends for this function like this @fields.depends('bar')
for ex:
@fields.depends('bar')
def on_change_foo(self):
if self.foo:
self.bar = 1
else:
self.bar += 1
Meaning if you change foo and it evaluates to True, 'bar' will be set to 1,
otherwise bar will increase by 1.
Here the you have to add in the depends any field you plan to use or modify
during the calculations.
It may look as a subtle difference in the beginning for an on_change_with*
where you update the value of one field when something else changes on the
record.
@fields.depends('bar')
def on_change_with_foo(self, name=None):
if self.bar ==100:
return True
return False
In this case, if bar changes, the method runs and the return value will be
updated to foo. Meaning foo will always be False unless bar hits 100.
Here the values in the depends define when the function will run, but also
you have to put here any field you use in the calculation.
In both cases you can add several fields to the depends, separated by a
comma.
>
> Thanks in advance
>
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.
[1] -
http://doc.tryton.org/4.6/trytond/doc/ref/models/fields.html?highlight=function#function
[2] - http://hg.tryton.org/modules/sale/file/f4db203a1b9f/sale.py#l147
[3] - http://hg.tryton.org/modules/sale/file/f4db203a1b9f/sale.py#l458
--
-------------------------
Karla Mª Stenger Sábat
[email protected]
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