Added ability to register fields to models

categories/__init__.py

@@ -0,0 +1,18 @@
+import fields
+import models
+
+from django.db.models import FieldDoesNotExist
+
+def register_m2m(model, field_name, extra_params={}):
+    return _register(model, field_name, extra_params, fields.CategoryM2MField)
+
+
+def register_fk(model, field_name, extra_params={}):
+    return _register(model, field_name, extra_params, fields.CategoryFKField)
+
+def _register(model, field_name='category', extra_params={}, field=fields.CategoryFKField):
+    opts = model._meta
+    try:
+        opts.get_field(field_name)
+    except FieldDoesNotExist:
+        field(**extra_params).contribute_to_class(model, field_name)

categories/fields.py

@@ -0,0 +1,11 @@
+from django.db.models import ForeignKey, ManyToManyField
+from categories.models import Category
+
+class CategoryM2MField(ManyToManyField):
+    def __init__(self, **kwargs):
+        super(CategoryM2MField, self).__init__(to=Category, **kwargs)
+
+
+class CategoryFKField(ForeignKey):
+    def __init__(self, **kwargs):
+        super(CategoryFKField, self).__init__(to=Category, **kwargs)