Move statement sum and diff to properties instead of model fields

Fix #32

nummi/statement/migrations/0003_remove_statement_diff_remove_statement_sum.py

@@ -0,0 +1,20 @@
+# Generated by Django 4.2 on 2025-01-03 13:23
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("statement", "0002_alter_statement_table"),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name="statement",
+            name="diff",
+        ),
+        migrations.RemoveField(
+            model_name="statement",
+            name="sum",
+        ),
+    ]

nummi/statement/models.py

@@ -4,7 +4,7 @@ from uuid import uuid4
 
 from account.models import AccountModel
 from django.core.validators import FileExtensionValidator
-from django.db import models, transaction
+from django.db import models
 from django.urls import reverse
 from django.utils.translation import gettext_lazy as _
 from media.utils import get_path
@@ -22,20 +22,6 @@ class Statement(AccountModel):
     start_value = models.DecimalField(
         max_digits=12, decimal_places=2, default=0, verbose_name=_("Start value")
     )
-    diff = models.DecimalField(
-        max_digits=12,
-        decimal_places=2,
-        default=0,
-        verbose_name=_("Difference"),
-        editable=False,
-    )
-    sum = models.DecimalField(
-        max_digits=12,
-        decimal_places=2,
-        default=0,
-        verbose_name=_("Transaction difference"),
-        editable=False,
-    )
     file = models.FileField(
         upload_to=get_path,
         validators=[FileExtensionValidator(["pdf"])],
@@ -54,21 +40,17 @@ class Statement(AccountModel):
             if _prever.file and _prever.file != self.file:
                 Path(_prever.file.path).unlink(missing_ok=True)
 
-        with transaction.atomic():
-            for trans in self.transaction_set.all():
-                trans.save()
-
-        self.diff = self.value - self.start_value
-        self.sum = (
-            self.transaction_set.aggregate(sum=models.Sum("value")).get("sum", 0) or 0
-        )
         super().save(*args, **kwargs)
 
-    def update_sum(self):
-        self.sum = (
-            self.transaction_set.aggregate(sum=models.Sum("value")).get("sum", 0) or 0
+    @property
+    def sum(self):
+        return self.transaction_set.aggregate(sum=models.Sum("value", default=0)).get(
+            "sum"
         )
-        super().save()
+
+    @property
+    def diff(self):
+        return self.value - self.start_value
 
     def delete(self, *args, **kwargs):
         if self.file: