fix issue #71

ormar/fields/foreign_key.py

@@ -1,3 +1,4 @@
+import uuid
 from typing import Any, List, Optional, TYPE_CHECKING, Type, Union
 
 import sqlalchemy
@@ -123,6 +124,8 @@ class ForeignKeyField(BaseField):
     def _construct_model_from_pk(
         cls, value: Any, child: "Model", to_register: bool
     ) -> "Model":
+        if cls.to.pk_type() == uuid.UUID and isinstance(value, str):
+            value = uuid.UUID(value)
         if not isinstance(value, cls.to.pk_type()):
             raise RelationshipInstanceError(
                 f"Relationship error - ForeignKey {cls.to.__name__} "

tests/test_uuid_fks.py

@@ -0,0 +1,67 @@
+import uuid
+
+import databases
+import pytest
+import sqlalchemy
+from sqlalchemy import create_engine
+
+import ormar
+from tests.settings import DATABASE_URL
+
+metadata = sqlalchemy.MetaData()
+db = databases.Database(DATABASE_URL)
+
+
+class User(ormar.Model):
+    class Meta:
+        tablename = "user"
+        metadata = metadata
+        database = db
+
+    id: uuid.UUID = ormar.UUID(
+        primary_key=True, default=uuid.uuid4, uuid_format="string"
+    )
+    username = ormar.String(index=True, unique=True, null=False, max_length=255)
+    email = ormar.String(index=True, unique=True, nullable=False, max_length=255)
+    hashed_password = ormar.String(null=False, max_length=255)
+    is_active = ormar.Boolean(default=True, nullable=False)
+    is_superuser = ormar.Boolean(default=False, nullable=False)
+
+
+class Token(ormar.Model):
+    class Meta:
+        tablename = "token"
+        metadata = metadata
+        database = db
+
+    id = ormar.Integer(primary_key=True)
+    text = ormar.String(max_length=4, unique=True)
+    user = ormar.ForeignKey(User, related_name="tokens")
+    created_at = ormar.DateTime(server_default=sqlalchemy.func.now())
+
+
+@pytest.fixture(autouse=True, scope="module")
+def create_test_database():
+    engine = create_engine(DATABASE_URL)
+    metadata.create_all(engine)
+    yield
+    metadata.drop_all(engine)
+
+
+@pytest.mark.asyncio
+async def test_uuid_fk():
+    async with db:
+        async with db.transaction(force_rollback=True):
+            user = await User.objects.create(
+                username="User1",
+                email="email@example.com",
+                hashed_password="^$EDACVS(&A&Y@2131aa",
+                is_active=True,
+                is_superuser=False,
+            )
+            await Token.objects.create(text="AAAA", user=user)
+            page_size = 20
+            page_num = 0
+            await Token.objects.order_by("-created_at").limit(page_size).offset(
+                page_size * (page_num - 1)
+            ).all()