Add customizable default value for TranslationHybrid

CHANGES.rst

@@ -4,6 +4,12 @@ Changelog
 Here you can see the full list of changes between each SQLAlchemy-Utils release.
 
 
+0.29.6 (2015-02-03)
+^^^^^^^^^^^^^^^^^^^
+
+- Added customizable TranslationHybrid default value
+
+
 0.29.5 (2015-02-03)
 ^^^^^^^^^^^^^^^^^^^
 

docs/internationalization.rst

@@ -90,4 +90,29 @@ Translation hybrids can also be used as expressions.
 
     session.query(Article).filter(Article.name['en'] == 'Some article')
 
+
+By default if no value is found for either current or default locale the
+translation hybrid returns `None`. You can customize this value with `default_value` parameter
+of translation_hybrid. In the following example we make translation hybrid fallback to empty string instead of `None`.
+
+::
+
+    translation_hybrid = TranslationHybrid(
+        current_locale=get_locale,
+        default_locale='en',
+        default_value=''
+    )
+
+
+    class Article(Base):
+        __tablename__ = 'article'
+
+        id = Column(Integer, primary_key=True)
+        name_translations = Column(HSTORE)
+
+        name = translation_hybrid(name_translations, default)
+
+
+    Article().name  # ''
+
 .. _SQLAlchemy-i18n: https://github.com/kvesteri/sqlalchemy-i18n

sqlalchemy_utils/__init__.py

@@ -87,7 +87,7 @@ from .types import (
 from .models import Timestamp
 
 
-__version__ = '0.29.5'
+__version__ = '0.29.6'
 
 
 __all__ = (

sqlalchemy_utils/i18n.py

@@ -26,9 +26,10 @@ except ImportError:
 
 
 class TranslationHybrid(object):
-    def __init__(self, current_locale, default_locale):
+    def __init__(self, current_locale, default_locale, default_value=None):
         self.current_locale = current_locale
         self.default_locale = default_locale
+        self.default_value = default_value
 
     def cast_locale(self, obj, locale):
         """
@@ -60,7 +61,7 @@ class TranslationHybrid(object):
                 try:
                     return getattr(obj, attr.key)[default_locale]
                 except (TypeError, KeyError):
-                    return None
+                    return self.default_value
         return getter
 
     def setter_factory(self, attr):

tests/test_translation_hybrid.py

@@ -33,6 +33,11 @@ class TestTranslationHybrid(TestCase):
         city = self.City()
         assert city.name is None
 
+    def test_custom_default_value(self):
+        self.translation_hybrid.default_value = 'Some value'
+        city = self.City()
+        assert city.name is 'Some value'
+
     def test_fall_back_to_default_translation(self):
         city = self.City(name_translations={'en': 'Helsinki'})
         self.translation_hybrid.current_locale = 'sv'