Added some docs and testing apps

docs/registering_models.rst

@@ -17,8 +17,25 @@ categories.register_m2m(MyModel)
 
 If you want more than one field on a model you have to have some extra arguments
 
-import categories
-categories.register_fk(MyModel, 'primary_category')
-categories.register_fk(MyModel, 'secondary_category', {'related_name':'mymodel_sec_set'})
+	import categories
+	categories.register_fk(MyModel, 'primary_category')
+	categories.register_fk(MyModel, 'secondary_category', {'related_name':'mymodel_sec_set'})
 
-The ``extra_args`` allows you to specify the related_name of one of the fields so it doesn't clash.
+The ``extra_args`` allows you to specify the related_name of one of the fields so it doesn't clash.
+
+
+Extra fields with Many-to-Many Categories
+=========================================
+
+Occasionally you may want to add one or more fields to the categories you relate to a given model. For example, you may want an easy way to select one of the categories to be "primary." This requires a bit more work.
+
+1. Create the intermediary class::
+
+	from categories.models import CategoryIntermediary
+	
+	# We're assuming that there is a ``Blog`` model previously defined 
+	# or imported
+	class BlogCategories(CategoryIntermediary):
+		blog = models.ForeignKey(Blog)
+	
+	categories.register_m2m(Blog, extra_args={'through':'BlogCategories'})

sample/simpletext/admin.py

@@ -1,4 +1,9 @@
 from models import SimpleText
 from django.contrib import admin
 
-admin.site.register(SimpleText)
+
+class SimpleTextAdmin(admin.ModelAdmin):
+    filter_horizontal = ['cats',]
+
+
+admin.site.register(SimpleText, SimpleTextAdmin)

sample/simpletext/models.py

@@ -27,5 +27,9 @@ class SimpleText(models.Model):
         return ('simpletext_detail_view_name', [str(self.id)])
     
 import categories
+from categories.models import CategoryIntermediary
+class SimpleTextCategories(CategoryIntermediary):
+	simpletext = models.ForeignKey(SimpleText)
+
 categories.register_fk(SimpleText, 'primary_category', {'related_name':'simpletext_primary_set'})
-categories.register_m2m(SimpleText, 'cats')
+categories.register_m2m(SimpleText, 'cats', )