Add ReprMixin and various getter mixins

src/pyramid_basemodel/mixin.py

@@ -6,6 +6,13 @@
     'PolymorphicBaseMixin',
     'PolymorphicMixin',
     'TouchMixin',
+    'GetByAttrMixin,',
+    'GetByIdMixin',
+    'GetBySlugMixin',
+    'GetByTitleMixin',
+    'GetByNameMixin',
+    'GetByEmailMixin',
+    'ReprMixin',
 ]
 
 import logging
@@ -50,7 +57,6 @@ def __mapper_args__(self):
         """Set the ``polymorphic_identity`` value to the lower case class name."""
 
         return {'polymorphic_identity': self.__class__.__name__.lower()}
-
 
 
 class TouchMixin(object):
@@ -80,5 +86,129 @@ def touch(self, propagate=True, now=None, save=None):
         # Call propagate touch.
         if propagate:
             self.propagate_touch()
-
 
+
+sentinel = object()
+
+
+class GetByAttrMixin(object):
+    """A mixin for adding ``by_attr`` helper to models."""
+
+    def by_attr(cls, attr, value):
+        """Get a Model object by one of its attributes.
+
+        Return ``None`` if the object is not found.
+        """
+        return cls.query.filter(getattr(cls, attr)==value).first()
+
+class GetByIdMixin(GetByAttrMixin):
+    """A mixin for adding ``by_id`` helper to models."""
+
+    @classmethod
+    def by_id(cls, id, default=sentinel):
+        """Get a Model object by its id.
+
+        Return ``None`` if the object is not found.
+        On error raise exception or return `default`, if it is set.
+        """
+        try:
+            id = int(id)
+            return cls.by_attr('id', id)
+        except (ValueError, TypeError) as exc:
+            if default == sentinel:
+                raise exc
+            else:
+                return default
+
+
+class GetBySlugMixin(GetByAttrMixin):
+    """A mixin for adding ``by_slug`` helper to models."""
+
+    @classmethod
+    def by_slug(cls, slug, default=sentinel):
+        """Get a Model object by its slug.
+
+        Return ``None`` if the object is not found.
+        On Unicode error raise exception or return `default`, if it is set.
+        """
+        try:
+            str(slug).decode('ascii')
+            return cls.by_attr('slug', slug)
+        except UnicodeDecodeError as exc:
+            if default == sentinel:
+                raise exc
+            else:
+		return default
+
+
+class GetByTitleMixin(GetByAttrMixin):
+    """A mixin for adding ``by_title`` helper to models."""
+
+    @classmethod
+    def by_title(cls, title, default=sentinel):
+        """Get a Model object by its title.
+
+        Return ``None`` if the object is not found.
+        On Unicode error raise exception or return `default`, if it is set.
+        """
+        try:
+            str(title).decode('ascii')
+            return cls.by_attr('title', title)
+        except UnicodeDecodeError as exc:
+            if default == sentinel:
+                raise exc
+            else:
+                return default
+
+
+class GetByNameMixin(GetByAttrMixin):
+    """A mixin for adding by_name method to models."""
+
+    @classmethod
+    def by_name(cls, name):
+        """Get a Model object by name.
+
+        Return ``None`` if the object is not found.
+        """
+
+        return cls.by_attr('name', name)
+
+
+class GetByEmailMixin(GetByAttrMixin):
+    """A mixin for adding ``by_email`` helper to models."""
+
+    @classmethod
+    def by_email(cls, email):
+        """Get a Model object by its email.
+
+        Return ``None`` if the object is not found.
+        """
+        return cls.by_attr('email', email)
+
+
+class ReprMixin(object):
+    """Provides a generic ``__repr__`` implementation."""
+
+    def __repr__(self):
+        """Return a generic string representation of a class.
+
+        The following format is used: '<class_name:id (field=value...)>.
+        Only name, title, slug, email fields are included in the string.
+        """
+        cls = type(self)
+        fields = ['name', 'title', 'slug', 'email']
+        formatted_fields = []
+        class_name = cls.__name__
+        id = cls.__dict__.get('id', None)
+
+        for field_name in fields:
+            try:
+                field_value = cls.__dict__[field_name]
+            except KeyError:
+                continue
+            if field_value:
+                field_value = field_value.encode('utf-8')
+            formatted_fields.append('{}={}, '.format(field_name, field_value))
+        concat_fields = ''.join(formatted_fields)[:-2]
+
+        return '<{}:{} ({})>'.format(class_name, id, concat_fields)