How do I set a value on a selection via a button - odoo-14

Question

I need to create a button which will define a ticket the value of the state variable to cloturé.
And when a ticket is cloturé, it will on read only.
How can i do it ?
The ticket's model is helpdesk.ticket
view.xml :
<?xml version='1.0' encoding='UTF-8'?>
<odoo>
<record id="helpdesk_ticket_view_form_inherit_header_modifie" model="ir.ui.view">
<field name="name">helpdesk.ticket.modifie.header</field>
<field name="model">helpdesk.ticket</field>
<field name="inherit_id" ref="helpdesk_fsm.helpdesk_ticket_view_form" />
<field name="arch" type="xml">
<xpath expr="//button[#name='action_generate_fsm_task']" position="attributes" >
<attribute name="string">Planifier tache</attribute>
</xpath>
</field>
</record>
</odoo>
ticket.py :
# -*- coding: utf-8 -*-
from odoo import models, fields, api
class ticket_inherit(models.Model):
_inherit = "helpdesk.ticket"
state = fields.Selection(['test','annulé','cloturé'],'selection')
#What i want to do
def cloture_le_ticket(self):
state = 'cloturé'

Answer 1

You can just use write().
state = fields.Selection(string="State", selection=[
('test', 'Test),
('annulé', 'Annulé'),
('cloturé', 'Cloturé')
])
def cloture_le_ticket(self):
self.write({
'state': 'cloturé'
})
To force the ticket to be read-only:
def write(self, vals):
for record in self:
if record.state == 'cloturé':
raise exceptions.UserError("Sorry but the ticket is read only")
return super(HelpdeskTicket, self).write(vals)