Hello, I have Odoo8.

Sorry if my question is very simple, but I can't find my mistake.

In a model (sale.order), I have a related field:

acopiado_restante = fields.Float(digits=(8,2), related='pricelist_version_id.monto_acopiado_restante', string="Monto acopiado restante")

The field points to a computed field on model product.pricelist.version.

In a method of sale.order class, I need to use the value of field 'acopiado_restante', specifically in this method:

def onchange_pricelist_id(self, cr, uid, ids, pricelist_id, order_lines, context=None): ...

I try to access to the field using self.acopiado_restante, but I get the error 'sale.order don't have field _ids'.

What is the mistake and how can access to the field? Thanks!