Onchange Method

Using @api.onchange to React to Field Changes

When a field value is modified from the frontend (such as through the user interface), it can trigger a function that performs specific operations in response to that change. This reactive behavior is often handled using Odoo’s @api.onchange decorator. Let’s illustrate this with an example.

Consider a model which contains patients' OP details:

class OpDetails(models.Model):
    _name = "op.details"
    _description = "Op Details"

    partner_id = fields.Many2one('res.partner', string="Patient Name", help="Select the patient")
    phone = fields.Integer(string="Phone", help="Patient's Phone number")
    email = fields.Char(string="Email Address", help="Patient's email")

Now, let’s define a function that is triggered when the partner_id field is modified. Upon selecting or changing the partner_id, we want the system to automatically populate the phone and email fields of the current record with the corresponding values from the selected partner’s contact information.

@api.onchange('partner_id')
def _onchange_partner_id(self):
    """ Update phone and email while changing the partner_id """
    self.write({
        'phone': self.partner_id.phone,
        'email': self.partner_id.email
    })

In this example, we use the @api.onchange() method decorator, passing partner_id as its argument. This means the function will be automatically triggered whenever the partner_id field is modified from the frontend.

Inside the function, you can define the logic that should execute in response to the change. Additionally, you can pass multiple fields to the @api.onchange() decorator. In that case, the method will be triggered whenever any of the specified fields are changed by the user.