On Tuesday 01 July 2008 11:29:56 Oleg Broytmann wrote:
> On Thu, Feb 14, 2008 at 07:31:10PM +0300, Oleg Broytmann wrote:
> > DecimalCol will not be changed. I will add documentation explaining
> > the type affinity problem in SQLite.
> > There will be a new DecimalStringCol that stores Decimals as text.
>
> It is now in the trunk.
>
> > If
> > you want quantization please write a validator class, and I will include
> > it into SQLObject. Initially it will be off, but a user can easily use it
> > - every column has a "validator" keyword argument.
>
> Oleg.
Oleg,
Thank you. I'd be happy to write a validator, if I can figure out how it
should work.
For the special case of CurrencyCol, which has precision known in advance,
this is easy:
=====
class CurrencyValidator(sqlobject.col.DecimalValidator):
HUNDREDTHS = Decimal('9.99')
def to_python(self, value, state):
value = super(CurrencyValidator, self).to_python(value, state)
if isinstance(value, Decimal):
value = value.quantize(self.HUNDREDTHS)
return value
def from_python(self, value, state):
value = super(CurrencyValidator, self).from_python(value, state)
if isinstance(value, Decimal):
value = value.quantize(self.HUNDREDTHS)
return value
======
But for a general DecimalCol, where the precision isn't known in advance,
obviously this simple strategy won't work.
An alternative strategy would be like this:
======
class PreciseDecimalValidator(sqlobject.col.DecimalValidator):
def __init__(self, *args, **kw):
size = kw.pop('size', None)
precision = kw.pop('precision', None)
if precision:
self.PRECISION = Decimal(10) ** (-1 * int(precision))
super(PreciseDecimalValidator, self).__init__(*args, **kw)
def to_python(self, value, state):
value = super(PreciseDecimalValidator, self).to_python(value, state)
if self.PRECISION and isinstance(value, Decimal):
value = value.quantize(self.PRECISION)
return value
def from_python(self, value, state):
value = super(PreciseDecimalValidator, self).from_python(value, state)
if self.PRECISION and isinstance(value, Decimal):
value = value.quantize(self.PRECISION)
return value
precision = 4
class Example(sqlobject.SQLObject):
value = sqlobject.DecimalCol(size=10, precision=precision,
validator=PreciseDecimalValidator(precision=precision))
=======
But this is very inelegant. Is there a way to use introspection instead?
Thanks,
cs
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