Add auto_now_add to last_updated field. Change updated_by to nullable

boards/migrations/0002_auto_20170917_1618.py

@@ -0,0 +1,27 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.4 on 2017-09-17 16:18
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('boards', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='post',
+            name='updated_by',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, related_name='+', to=settings.AUTH_USER_MODEL),
+        ),
+        migrations.AlterField(
+            model_name='topic',
+            name='last_updated',
+            field=models.DateTimeField(auto_now_add=True),
+        ),
+    ]

boards/models.py

@@ -12,7 +12,7 @@ def __str__(self):
 
 class Topic(models.Model):
     subject = models.CharField(max_length=255)
-    last_updated = models.DateTimeField()
+    last_updated = models.DateTimeField(auto_now_add=True)
     board = models.ForeignKey(Board, related_name='topics')
     starter = models.ForeignKey(User, related_name='topics')
 
@@ -23,4 +23,4 @@ class Post(models.Model):
     created_at = models.DateTimeField(auto_now_add=True)
     updated_at = models.DateTimeField(null=True)
     created_by = models.ForeignKey(User, related_name='posts')
-    updated_by = models.ForeignKey(User, related_name='+')
+    updated_by = models.ForeignKey(User, null=True, related_name='+')