Issue #22: Proposal for raise exception if default is not valid type.

Author: boonya

domain_models/fields.py

@@ -62,6 +62,13 @@ def set_value(self, model, value):
             value = self._converter(value)
         setattr(model, self.storage_name, value)
 
+    def is_valid_type(self, value):
+        """Check whether the value is valid type.
+
+        :param value:
+        """
+        return self._converter(value) == value
+
     def _converter(self, value):
         """Convert raw input value of the field."""
         return value

domain_models/models.py

@@ -185,10 +185,27 @@ def __data__(self):
                     for field in self.__class__.__fields__)
 
     def get(self, field_name, default=None):
-        """DomainModel analogue for dict.get python built-in method.
+        """Return the value of the field.
+
+        Analogue for `dict.get()` python method.
+        `field_name` must be a string. If the string is the name of
+        one of the existent fields, the result is the value of that field.
+        For example, `model.get('foobar')` is equivalent to `model.foobar`.
+        If the filed does not have a value, `default` is returned if provided.
+        It will raise `AttributeError` if `default` is not the same type
+        as field value.
+        If the field does not exist, `AttributeError` is raised as well.
 
         :param string field_name:
         :param mixed default:
         """
         value = getattr(self, field_name)
+
+        if default is not None and value is None:
+            field = dict((field.name, field) for field in
+                         self.__class__.__fields__).get(field_name)
+            if not field.is_valid_type(default):
+                raise AttributeError(
+                    "default must be the same type as the field.")
+
         return value if value else default

tests/test_models.py

@@ -165,28 +165,38 @@ class Model2(models.DomainModel):
                 field = Model1.field
 
     def test_get_method(self):
+        mock_id = 2
+        mock_name = 'foobar'
+
         class SomeModel(models.DomainModel):
             """Test domain model."""
             id = fields.Int()
             name = fields.String()
-            not_required = fields.String()
+            string = fields.String()
+
+        model = SomeModel(id=mock_id, name=mock_name)
 
-        model = SomeModel()
-        model.id = 2
-        model.name = 'some-name'
+        self.assertEqual(model.get('id'), mock_id)
+        self.assertEqual(model.get('id', 0), mock_id)
+        self.assertEqual(model.get('id', 123), mock_id)
 
-        id = model.get('id', 0)
-        self.assertEqual(id, 2)
+        self.assertEqual(model.get('name'), mock_name)
+        self.assertEqual(model.get('name', ''), mock_name)
+        self.assertEqual(model.get('name', 'another-name'), mock_name)
 
-        name = model.get('name', '')
-        self.assertEqual(name, 'some-name')
+        self.assertEqual(model.get('string'), None)
+        self.assertEqual(model.get('string', ''), '')
+        self.assertEqual(model.get('string', 'not-empty'), 'not-empty')
 
-        not_required = model.get('not_required', '')
-        self.assertEqual(not_required, '')
+        string = model.get('string', '')
+        self.assertEqual(string, '')
 
         with self.assertRaises(AttributeError):
             model.get('unknown')
 
+        with self.assertRaises(AttributeError):
+            model.get('string', 0)
+
 
 class ModelReprTests(unittest.TestCase):
     """Tests for model Pythonic representation."""