Why my compute field does not work on the reverse side?

Question

I have the computed field x_totalunity which depends on the fields product_uom_qty and x_unitparcarton.

What I want is to be able to write also any value in x_totalunity and that product_uom_qty changes due to this (product_uom_qty = x_totalunity / x_unitparcarton). But this does not work.

This is my code :

@api.depends('product_uom_qty', 'discount', 'price_unit', 'tax_id',
             'x_unitparcarton'  )
def _compute_amount(self):
"""
compute the amounts of the SO line.
"""
for line in self:
    line.x_totalunity = line.product_uom_qty * line.x_unitparcarton

x_totalunity = fields.Float(compute='_compute_amount', string='Total unitéé',
    readonly=False, store=True ,  required=True, copy=True)

Answer 1

First, remove discount, price_unit and tax_id from the @api.depends, as they seem to have no relevance in the computation of x_totalunity.

Then, I think you are looking for the parameter inverse, to perform some actions in case someone is modifying the computed field by hand:

@api.multi
@api.depends('product_uom_qty', 'x_unitparcarton')
def _compute_x_totalunity(self):
    """Compute the amounts of the SO line."""
    for line in self:
        line.x_totalunity = line.product_uom_qty * line.x_unitparcarton

@api.multi
def _inverse_x_totalunity(self):
    for line in self:
        line.product_uom_qty = line.x_totalunity / line.x_unitparcarton

x_totalunity = fields.Float(
    compute='_compute_x_totalunity',
    inverse='_inverse_x_totalunity',
    string='Total unitéé',
    required=True,
    readonly=False,
    store=True,
    copy=True,
)