Simple Multiplication of two fields in OpenErp

Question

I have two fields in a class, in a third field i need the multiplication result of the two fields declared before.

For example:

_columns = {
            'Item' : fields.integer('Items'),
            'Fecha': fields.date('Fecha del Documento', required=True, select=True),
            'Codigo Arancelario' : fields.integer('Codigo Arancelario'),
            'Descripcion Arancelaria' : fields.char('Descripcion Arancelaria', size=42, required = True, translate = True), 
            'Especificaciones Tecnicas' : fields.char('Especificaciones Tecnicas', size=60, required = True, translate = True), 
            'Cantidad' : fields.float('Cantidad'), 'Unidad de Medida': fields.many2one('product.uom', 'Unidad de Medida'),
            'Precio Unitario Declarado' : fields.float('Precio Unitario Declarado'), 'Moneda' : fields.many2one('res.currency', 'Moneda'),
            'Valor En Divisas' : Result of the multiplication of 'Precio Unitario Declarado' * 'Cantidad',
            'notas' : fields.text('Notas'),
            }

Should i use a function field for such a simple calculation?

Is there a simpler way to accomplish this?

Answer 1

function field will be the good option to do such kind of operation. here is the sample code for multiplication of two field using functional field.

def multi_a_b(self, cr, uid, ids, name, arg, context=None):
    res = {}
    for record in self.browse(cr, uid, ids,context):
        res[record.id] = record.field_a * record.field_b
    return res

_columns = {
    'field_a': fields.integer('A'),
    'field_b': fields.integer('B'),
    'field_c': fields.function(multi_a_b, type='integer', 'C'),
}

Answer 2

You need to do a combination of these answers.

First define c4 as a functional field as specified in the answer from user1576199, then create the on_change function as defined in the answer from Atul;

def onchange_value(self, cr, uid, ids, c1 = 0.0, c2 = 0.0, c3 = 0.0, context = None):
     return {'value': {'c4': c1 + c2 + c3}}

but, put the on_change on the values c1 to c3, not c4, like this...

 <field name="c1" on_change="onchange_value(c1, c2, c3, context) />
 <field name="c2" on_change="onchange_value(c1, c2, c3, context)/>
 <field name="c3" on_change="onchange_value(c1, c2, c3, context)/>
 <field name="c4" />

c4 is a functional field but you can still return it in an on_change value clause for other field(s) and the value on the screen will be refreshed but it will not be stored in the database unless you add store = True to the c4 field definition.

If the user changes any of the c1, c2 or c3 fields, the on_change method will be called and the total will be re-calculated and refreshed on the display.

Answer 3

Here is possible solution

from osv import osv, fields

def multi_price_qty(self, cr, uid, ids, name, arg, context=None):
    res = {}
    for product in self.browse(cr, uid, ids,context):
        res[product.id] = product.price * product.qty
    return res

class abs_product(osv.Model):
    _name = "abs.product"
    _columns = {
    'code': fields.char('Code', size=32),
    'description': fields.char('Description', size=64),
    'sizeunit': fields.char('Size /Unit', size=32),
    'qty': fields.integer('Quantity', size=32),
    'price': fields.integer('Price'),
    'pullout': fields.char('Pull-Out', size=32),
    'return': fields.char('Return', size=32),
    'offtake': fields.char('Offtake', size=32),
    'weeksales': fields.char('Weekly Sales', size=32),
    'date': fields.date('Date'),
    'totalprice': fields.function(multi_price_qty, type='integer', 'Total Price'),
    }
abs_product()

Answer 4

I think function field is ok for this type of calculation.

OR another way you can put a button, on button click multiply this two filed values.