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--- django [2026/03/27 00:36] – Create Django snippets page with common patterns roger
+++ django [2026/03/27 00:52] (current) – Add migrations, signals, and DRF sections roger
@@ Line 165: / Line 165: @@
 </code>
+===== Migrations =====
+==== Squash migrations ====
+<code bash>
+python manage.py squashmigrations myapp 0001 0015
+</code>
+==== Create an empty migration (for data migrations) ====
+<code bash>
+python manage.py makemigrations myapp --empty -n my_data_migration
+</code>
+==== Data migration template ====
+<code python>
+from django.db import migrations
+def forwards(apps, schema_editor):
+    MyModel = apps.get_model("myapp", "MyModel")
+    for obj in MyModel.objects.filter(status="old"):
+        obj.status = "new"
+        obj.save(update_fields=["status"])
+def backwards(apps, schema_editor):
+    pass  # or reverse the migration
+class Migration(migrations.Migration):
+    dependencies = [
+        ("myapp", "0015_previous"),
+    ]
+    operations = [
+        migrations.RunPython(forwards, backwards),
+    ]
+</code>
+===== Signals =====
+==== Post-save signal ====
+<code python>
+from django.db.models.signals import post_save
+from django.dispatch import receiver
+@receiver(post_save, sender=User)
+def create_profile(sender, instance, created, **kwargs):
+    if created:
+        Profile.objects.create(user=instance)
+</code>
+===== Django REST Framework =====
+==== Serializer with nested write support ====
+<code python>
+class AddressSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = Address
+        fields = ["street", "city", "country"]
+class UserSerializer(serializers.ModelSerializer):
+    address = AddressSerializer()
+    class Meta:
+        model = User
+        fields = ["name", "email", "address"]
+    def create(self, validated_data):
+        address_data = validated_data.pop("address")
+        user = User.objects.create(**validated_data)
+        Address.objects.create(user=user, **address_data)
+        return user
+</code>
+==== Custom permission ====
+<code python>
+from rest_framework.permissions import BasePermission
+class IsOwner(BasePermission):
+    def has_object_permission(self, request, view, obj):
+        return obj.owner == request.user
+</code>
+==== Pagination ====
+<code python>
+# settings.py
+REST_FRAMEWORK = {
+    "DEFAULT_PAGINATION_CLASS": "rest_framework.pagination.PageNumberPagination",
+    "PAGE_SIZE": 25,
+}
+# Or custom pagination
+from rest_framework.pagination import CursorPagination
+class CreatedAtCursorPagination(CursorPagination):
+    ordering = "-created_at"
+    page_size = 50
+</code>
 ===== See Also =====
   * [[django:links|Django Links]] - Useful Django resources and references