Use Signal to calculate Priority

backend/tasks/apps.py

@@ -4,3 +4,6 @@ from django.apps import AppConfig
 class TasksConfig(AppConfig):
     default_auto_field = 'django.db.models.BigAutoField'
     name = 'tasks'
+
+    def ready(self):
+        import tasks.signals

backend/tasks/models.py

@@ -68,27 +68,8 @@ class Todo(Todo):
 
     priority = models.PositiveSmallIntegerField(choices=EisenhowerMatrix.choices, default=EisenhowerMatrix.NOT_IMPORTANT_NOT_URGENT)
 
-    def calculate_eisenhower_matrix_category(self):
+    def __str__(self):
-        if self.end_event:
+        return self.title
-            time_until_due = (self.end_event - timezone.now()).days
-        else:
-            time_until_due = float('inf')
-
-        urgency_threshold = 3
-        importance_threshold = 3
-
-        if time_until_due <= urgency_threshold and self.importance >= importance_threshold:
-            return Todo.EisenhowerMatrix.IMPORTANT_URGENT
-        elif time_until_due > urgency_threshold and self.importance >= importance_threshold:
-            return Todo.EisenhowerMatrix.IMPORTANT_NOT_URGENT
-        elif time_until_due <= urgency_threshold and self.importance < importance_threshold:
-            return Todo.EisenhowerMatrix.NOT_IMPORTANT_URGENT
-        else:
-            return Todo.EisenhowerMatrix.NOT_IMPORTANT_NOT_URGENT
-
-    def save(self, *args, **kwargs):
-        self.priority = self.calculate_eisenhower_matrix_category()
-        super(Todo, self).save(*args, **kwargs)
 
 
 class Subtask(models.Model):

backend/tasks/signals.py

@@ -0,0 +1,25 @@
+from django.db.models.signals import pre_save
+from django.dispatch import receiver
+from django.utils import timezone
+
+from tasks.models import Todo
+
+
+@receiver(pre_save, sender=Todo)
+def update_priority(sender, instance, **kwargs):
+    if instance.end_event:
+        time_until_due = (instance.end_event - timezone.now()).days
+    else:
+        time_until_due = float('inf')
+
+    urgency_threshold = 3
+    importance_threshold = 3
+
+    if time_until_due <= urgency_threshold and instance.importance >= importance_threshold:
+        instance.priority = Todo.EisenhowerMatrix.IMPORTANT_URGENT
+    elif time_until_due > urgency_threshold and instance.importance >= importance_threshold:
+        instance.priority = Todo.EisenhowerMatrix.IMPORTANT_NOT_URGENT
+    elif time_until_due <= urgency_threshold and instance.importance < importance_threshold:
+        instance.priority = Todo.EisenhowerMatrix.NOT_IMPORTANT_URGENT
+    else:
+        instance.priority = Todo.EisenhowerMatrix.NOT_IMPORTANT_NOT_URGENT