Duration fail

models/event.py

@@ -17,7 +17,7 @@ class Event(models.Model):
     date_start = fields.Date(default=fields.Date.context_today, required=True)
     date_end = fields.Date(required=True)
 
-    duration = fields.Float()
+    duration = fields.Float(compute='_compute_duration')
 
 
     @api.constrains('date_end')
@@ -26,9 +26,8 @@ class Event(models.Model):
         if self.date_start > self.date_end:
             raise ValidationError(_('Date most be supperior to to start date'))
 
-    #
-    # @api.constrains('duration')
-    # def _check_duration(self):
-    #     """Calcul du temps entre date_start et date_end ne heure"""
-    #     for event in self:
-    #         self.date_start.hour - self.date_end-hour:
+
+    @api.depends('date_start', 'date_end')
+    def _compute_duration(self):
+        for event in self:
+            event.duration = event.date_end - event.date_start

views/event_views.xml

@@ -14,7 +14,7 @@
               <!-- <field name="manager" /> -->
               <field name="date_start" />
               <field name="date_end" />
-              <field name="duration" />
+              <field name="duration" readonly="1" />
             </group>
           </group>
         </sheet>