Ensured hidden asset fields are completed on every database write

assets/management/commands/generateSampleAssetsData.py

@@ -1,7 +1,6 @@
 import random
 from django.core.management.base import BaseCommand, CommandError
 from django.utils import timezone
-
 from assets import models
 
 
@@ -96,8 +95,9 @@ class Command(BaseCommand):
                 cores=random.choice(circuits)
             )
 
-            prefix = random.choice(asset_prefixes)
+            if i % 5 == 0:
-            asset.asset_id = prefix + str(models.Asset.get_available_asset_id(wanted_prefix=prefix))
+                prefix = random.choice(asset_prefixes)
+                asset.asset_id = prefix + str(models.Asset.get_available_asset_id(wanted_prefix=prefix))
 
             if i % 4 == 0:
                 asset.parent = models.Asset.objects.order_by('?').first()

assets/migrations/0008_auto_20191205_1937.py

@@ -1,11 +1,8 @@
-# Generated by Django 2.0.13 on 2019-12-05 16:53
+# Generated by Django 2.0.13 on 2019-12-05 19:37
-# Edited by Matthew Smith on same date.
 
 import re
 from django.db import migrations, models
-from django.db import migrations, models
+import django.db.migrations
-import django.db.migrations.operations.special
-
 
 def forwards(apps, schema_editor):
     AssetModel = apps.get_model('assets', 'Asset')
@@ -25,8 +22,6 @@ def forwards(apps, schema_editor):
 
 class Migration(migrations.Migration):
 
-    replaces = [('assets', '0008_auto_20191205_1354'), ('assets', '0009_auto_20191205_1652')]
-
     dependencies = [
         ('assets', '0007_auto_20190108_0202_squashed_0014_auto_20191017_2052'),
     ]
@@ -35,14 +30,12 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='asset',
             name='asset_id_number',
-            field=models.IntegerField(default=0),
+            field=models.IntegerField(default=1),
-            preserve_default=False,
         ),
         migrations.AddField(
             model_name='asset',
             name='asset_id_prefix',
-            field=models.CharField(default=0, max_length=5),
+            field=models.CharField(default='', max_length=5),
-            preserve_default=False,
         ),
         migrations.RunPython(
             code=forwards,

assets/models.py

@@ -3,6 +3,9 @@ from django.core.exceptions import ValidationError
 from django.db import models, connection
 from django.urls import reverse
 
+from django.db.models.signals import pre_save
+from django.dispatch.dispatcher import receiver
+
 
 class AssetCategory(models.Model):
     class Meta:
@@ -85,8 +88,8 @@ class Asset(models.Model):
 
     # Hidden asset_id components
     # For example, if asset_id was "C1001" then asset_id_prefix would be "C" and number "1001"
-    asset_id_prefix = models.CharField(max_length=5)
+    asset_id_prefix = models.CharField(max_length=5, default="")
-    asset_id_number = models.IntegerField()
+    asset_id_number = models.IntegerField(default=1)
 
     def get_available_asset_id(wanted_prefix=""):
         sql = """
@@ -120,11 +123,9 @@ class Asset(models.Model):
             errdict["date_sold"] = ["Cannot sell an item before it is acquired"]
 
         self.asset_id = self.asset_id.upper()
-        asset_search = re.search("^([A-Z0-9]*?[A-Z]?)([0-9]+)$", self.asset_id)
+        asset_search = re.search("^([a-zA-Z0-9]*?[a-zA-Z]?)([0-9]+)$", self.asset_id)
         if asset_search is None:
-                errdict["asset_id"] = ["An Asset ID can only consist of letters and numbers"]
+                errdict["asset_id"] = ["An Asset ID can only consist of letters and numbers, with a final number"]
-        self.asset_id_prefix = asset_search.group(1)
-        self.asset_id_number = int(asset_search.group(2))
 
         if self.purchase_price and self.purchase_price < 0:
             errdict["purchase_price"] = ["A price cannot be negative"]
@@ -148,3 +149,14 @@ class Asset(models.Model):
 
         if errdict != {}:  # If there was an error when validation
             raise ValidationError(errdict)
+
+
+@receiver(pre_save, sender=Asset)
+def pre_save_asset(sender, instance, **kwargs):
+    """Automatically fills in hidden members on database access"""
+    asset_search = re.search("^([a-zA-Z0-9]*?[a-zA-Z]?)([0-9]+)$", instance.asset_id)
+    if asset_search is None:
+        instance.asset_id += "1"
+    asset_search = re.search("^([a-zA-Z0-9]*?[a-zA-Z]?)([0-9]+)$", instance.asset_id)
+    instance.asset_id_prefix = asset_search.group(1)
+    instance.asset_id_number = int(asset_search.group(2))