Odoo force a field higher than x - odoo

Question

In sales order, there is a field discount %. Is it possible to ensure the users only input value lower than x and it will not accept any value higher than x.

Answer 1

You can achieve this with creating a function using #api.onchange('discount') decorator on python code to ensure discount value is not higher than x, if higher then set x to discount field and also possible to show warning popup from that function.
But if python code change is not prefered, you can also achieve this with Automated action where you create a new rule on sale.order.line, set trigger On form modification, action Execute python code and add the following code
if record.discount > 10:
record.discount = 10
Where 10 is the value of x. This will ensure discount is always less than x.

Answer 2

Op1: If you want to ensure that behaviour you can add an sql constraint to the database, this will work fine if your X value never change, something like this:
_sql_constraints = [
('discount_less_than_X', 'CHECK(discount < X)', 'The discount value should be less than X'),
]
This constraint will trigger in all cases(create, write, import, SQL insert).
Replace X with the value desired.
Op2: Use decorator api.constrains, get X value from somewherelse and apply the restriccion, something like this:
#api.constrains('discount')
def _check_discount(self):
# Create a key:value parameter in `ir.config_parameter` table before.
disscount_max_value = self.env['ir.config_parameter'].sudo().get_param('disscount_max_value')
for rec in self:
if rec.disscount > int(disscount_max_value):
raise ValidationError('The discount value should be less than {}'.format(disscount_max_value))
I hope this answer can be helful for you.