feat: fields.MethodField

alcherializer/fields.py

@@ -84,3 +84,7 @@ def check_if_length_is_under_limit(
             return False, f"Limit of characters is {self.field.type.length}"
 
         return True, None
+
+
+class MethodField(BaseField):
+    pass

alcherializer/serializer.py

@@ -85,6 +85,19 @@ def _get_fields(self) -> Dict[str, Any]:
                 "validator": self._get_field_validator(key, value),
             }
 
+        for field in required_fields:
+            if field in columns:
+                continue
+
+            if not hasattr(self, field):
+                continue
+
+            columns[field] = {
+                "type": getattr(self, field),
+                "required": False,
+                "validator": self._get_field_validator(field, field),
+            }
+
         return columns
 
     def _get_field_validator(self, key: str, field):
@@ -107,6 +120,9 @@ def _get_field_validator(self, key: str, field):
         return fields.BaseField(key, field)
 
     def _get_instance_field_value(self, instance, field: str) -> Any:
+        if isinstance(self.fields[field].get("type"), fields.MethodField):
+            return getattr(self, f"get_{field}", lambda o: None)(instance)
+
         value = getattr(instance, field)
         if isinstance(value.__class__, DeclarativeMeta):
             serializer = self.fields[field]["validator"]

tests/unit/serializer/test_data.py

@@ -2,7 +2,10 @@
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.orm import relationship
 
-from alcherializer import Serializer
+from alcherializer import (
+    Serializer,
+    fields,
+)
 
 
 def test_data_single_instance() -> None:
@@ -171,3 +174,29 @@ class Meta:
             {"id": 1, "hello": "world"},
         ],
     }
+
+
+def test_data_get_method_fields() -> None:
+    class MyModel(declarative_base()):
+        id = sqlalchemy.Column(
+            sqlalchemy.Integer, primary_key=True, nullable=False
+        )
+        first_name = sqlalchemy.Column(sqlalchemy.String)
+        last_name = sqlalchemy.Column(sqlalchemy.String)
+
+        __tablename__ = "my_model"
+
+    class MyModelSerializer(Serializer):
+        full_name = fields.MethodField()
+
+        def get_full_name(self, obj: MyModel):
+            return f"{obj.first_name} {obj.last_name}"
+
+        class Meta:
+            model = MyModel
+            fields = ["id", "full_name"]
+
+    model = MyModel(id=1, first_name="hello", last_name="world")
+
+    serializer = MyModelSerializer(model)
+    assert serializer.data == {"id": 1, "full_name": "hello world"}