Dynamically set currency

[derenio]

One of our projects requires the currency of the PriceField to be dynamically set.
Our solution is to define get_currency method on the PriceField which can be overridden by class inheritance.
master...derenio:feature/dynamic_currency

Exemplary use case:

from django.db import models
from django_prices.models import PriceField


class DynamicPriceField(PriceField):

    def get_currency(self):
        if not self.currency:
            self.currency = self.model.currency
        return self.currency

class Purchase(models.Model):
    CURRENCY_CHOICES = [
        ('USD', 'USD'),
        ('GBP', 'GBP'),
        ('PLN', 'PLN')]

    currency = models.ChoiceField(choices=CURRENCY_CHOICES)
    price =     cost = DynamicPriceField(decimal_places=2, max_digits=10, default=Decimal())

[patrys]

I'd rather create a PriceAndCurrencyField that stores the currency in a database field.

[derenio]

Django still doesn't support the multiple db columns field:
https://code.djangoproject.com/ticket/5929
We will have to let programmers manually define the currency field and provide its name as a constructor's parameter in the price field.

[spout]

@derenio: same issue, so I've tried your example. I get Price instance without currency (Price('10', currency=None)).
(Using django-prices with django-prices-openexchangerates)

[derenio]

@spout my exemplary use case was based on my feature branch master...derenio:feature/dynamic_currency.
If you want to be able to have the currency based on a custom field (retrieved in the get_currency method) you will also have to override the changed to_python and formfield methods in the DynamicPriceField class (change self.currency to self.get_currency()):

class DynamicPriceField(PriceField):

    def get_currency(self):
        if not self.currency:
            self.currency = self.model.currency
        return self.currency

    def to_python(self, value):
        currency = self.get_currency()
        if isinstance(value, Price):
            if value.currency != currency:
                raise ValueError('Invalid currency: %r (expected %r)' % (
                    value.currency, currency))
            return value
        value = super(PriceField, self).to_python(value)
        if value is None:
            return value
        return Price(value, currency=currency)

    def formfield(self, **kwargs):
        defaults = {'currency': self.get_currency(),
                    'form_class': forms.PriceField}
        defaults.update(kwargs)
        return super(PriceField, self).formfield(**defaults)

[spout]

@derenio: Thank you !