Fixed #101. None will be displayed as empty string by default.

examples/sqla/simple.py

@@ -53,6 +53,7 @@ class Post(db.Model):
 class Tag(db.Model):
     id = db.Column(db.Integer, primary_key=True)
     name = db.Column(db.Unicode(64))
+    value = db.Column(db.Boolean())
 
     def __unicode__(self):
         return self.name

flask_admin/model/base.py

@@ -6,7 +6,7 @@ from flask.ext.admin.babel import gettext
 
 from flask.ext.admin.base import BaseView, expose
 from flask.ext.admin.tools import rec_getattr
-from flask.ext.admin.model import filters
+from flask.ext.admin.model import filters, typefmt
 from flask.ext.admin.actions import ActionsMixin
 
 
@@ -90,6 +90,35 @@ class BaseModelView(BaseView, ActionsMixin):
                 pass
     """
 
+    list_type_formatters = None
+    """
+        Dictionary of value type formatters to be used in list view.
+
+        By default, two types are formatted:
+        1. ``None`` will be displayed as empty string
+        2. ``bool`` will be displayed as checkbox
+
+        If you don't like default behavior and don't want any type formatters
+        applied, just override this property with empty dictionary::
+
+            class MyModelView(BaseModelView):
+                list_type_formatters = dict()
+
+        If you don't want to display `NULL` instead of empty string, you can do
+        something like this::
+
+            from flask.ext.admin import typefmt
+
+            MY_DEFAULT_FORMATTERS = dict(typefmt.DEFAULT_FORMATTERS).extend({
+                    type(None): typefmt.null_formatter
+                })
+
+            class MyModelView(BaseModelView):
+                list_type_formatters = MY_DEFAULT_FORMATTERS
+
+        Type formatters have lower priority than list column formatters.
+    """
+
     rename_columns = None
     """
         Dictionary where key is column name and value is string to display.
@@ -281,6 +310,10 @@ class BaseModelView(BaseView, ActionsMixin):
         # Filters
         self._filters = self.get_filters()
 
+        # Type formatters
+        if self.list_type_formatters is None:
+            self.list_type_formatters = dict(typefmt.DEFAULT_FORMATTERS)
+
         if self._filters:
             self._filter_groups = []
             self._filter_dict = dict()
@@ -707,10 +740,17 @@ class BaseModelView(BaseView, ActionsMixin):
             :param name:
                 Field name
         """
-        if name in self.list_formatters:
-            return self.list_formatters[name](context, model, name)
+        column_fmt = self.list_formatters.get(name)
+        if column_fmt is not None:
+            return column_fmt(context, model, name)
+
+        value = rec_getattr(model, name)
+
+        type_fmt = self.list_type_formatters.get(type(value))
+        if type_fmt is not None:
+            value = type_fmt(value)
 
-        return rec_getattr(model, name)
+        return value
 
     # Views
     @expose('/')

flask_admin/model/typefmt.py

+from jinja2 import Markup
+
+
+def null_formatter(value):
+    """
+        Return `NULL` as the string for `None` value
+
+        :param value:
+            Value to check
+    """
+    return Markup('<i>NULL</i>')
+
+
+def empty_formatter(value):
+    """
+        Return empty string for `None` value
+
+        :param value:
+            Value to check
+    """
+    return ''
+
+
+def bool_formatter(value):
+    """
+        Return check icon if value is `True` or empty string otherwise.
+
+        :param value:
+            Value to check
+    """
+    return Markup('<i class="icon-ok"></i>' if value else '')
+
+
+DEFAULT_FORMATTERS = {
+    type(None): empty_formatter,
+    bool: bool_formatter
+}