feat: add data initialization on model load

- Introduced `init_on_load` to handle JSON deserialization for fields using Pydantic models.
- Enhanced tests to verify the deserialization of complex fields in `ExampleWithId`.

Generated-by: aiautocommit

test/serialization_test.py

@@ -1,8 +1,11 @@
+from typing import get_args, get_origin
+
 from pydantic import BaseModel as PydanticBaseModel
 
 from activemodel import BaseModel
 from activemodel.mixins import TypeIDMixin
 from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.orm import reconstructor
 from sqlmodel import Field
 
 TYPEID_PREFIX = "myid"
@@ -18,6 +21,30 @@ class ExampleWithId(BaseModel, TypeIDMixin(TYPEID_PREFIX), table=True):
     object_field: SubObject = Field(sa_type=JSONB())
     unstructured_field: dict = Field(sa_type=JSONB())
 
+    @reconstructor
+    def init_on_load(self):
+        for field_name, field_info in self.model_fields.items():
+            raw_value = getattr(self, field_name, None)
+
+            if raw_value is None:
+                continue
+
+            annotation = field_info.annotation
+            origin = get_origin(annotation)
+            args = get_args(annotation)
+
+            # e.g. list[SomePydanticModel]
+            if origin is list and len(args) == 1:
+                model_cls = args[0]  # e.g. SomePydanticModel
+                if issubclass(model_cls, PydanticBaseModel) and isinstance(
+                    raw_value, list
+                ):
+                    parsed_value = [model_cls(**item) for item in raw_value]
+                    setattr(self, field_name, parsed_value)
+            # single model
+            elif issubclass(annotation, PydanticBaseModel):
+                setattr(self, field_name, annotation(**raw_value))
+
 
 def test_json_serialization(create_and_wipe_database):
     sub_object = SubObject(name="test", value=1)
@@ -29,4 +56,7 @@ def test_json_serialization(create_and_wipe_database):
 
     fresh_example = ExampleWithId.get(example.id)
 
-    breakpoint()
+    assert fresh_example is not None
+    assert isinstance(fresh_example.object_field, SubObject)
+    assert isinstance(fresh_example.list_field[0], SubObject)
+    assert isinstance(fresh_example.unstructured_field, dict)