Fixed #2265 -- Fixed problem with using iterators for "choices" attribute.

Thanks, Alex Dedul.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@3851 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/fields/__init__.py

@@ -5,6 +5,7 @@ from django.core import validators
 from django import forms
 from django.core.exceptions import ObjectDoesNotExist
 from django.utils.functional import curry
+from django.utils.itercompat import tee
 from django.utils.text import capfirst
 from django.utils.translation import gettext, gettext_lazy
 import datetime, os, time
@@ -80,7 +81,7 @@ class Field(object):
         self.prepopulate_from = prepopulate_from
         self.unique_for_date, self.unique_for_month = unique_for_date, unique_for_month
         self.unique_for_year = unique_for_year
-        self.choices = choices or []
+        self._choices = choices or []
         self.radio_admin = radio_admin
         self.help_text = help_text
         self.db_column = db_column
@@ -324,6 +325,14 @@ class Field(object):
     def bind(self, fieldmapping, original, bound_field_class):
         return bound_field_class(self, fieldmapping, original)
 
+    def _get_choices(self):
+        if hasattr(self._choices, 'next'):
+            choices, self._choices = tee(self._choices)
+            return choices
+        else:
+            return self._choices
+    choices = property(_get_choices)
+
 class AutoField(Field):
     empty_strings_allowed = False
     def __init__(self, *args, **kwargs):

django/utils/itercompat.py

@@ -0,0 +1,31 @@
+"""
+Providing iterator functions that are not in all version of Python we support.
+Where possible, we try to use the system-native version and only fall back to
+these implementations if necessary.
+"""
+
+import itertools
+
+def compat_tee(iterable):
+    """Return two independent iterators from a single iterable.
+
+    Based on http://www.python.org/doc/2.3.5/lib/itertools-example.html
+    """
+    # Note: Using a dictionary and a list as the default arguments here is
+    # deliberate and safe in this instance.
+    def gen(next, data={}, cnt=[0]):
+        dpop = data.pop
+        for i in count():
+            if i == cnt[0]:
+                item = data[i] = next()
+                cnt[0] += 1
+            else:
+                item = dpop(i)
+            yield item
+    next = iter(iterable).next
+    return gen(next), gen(next)
+
+if hasattr(itertools, 'tee'):
+    tee = itertools.tee
+else:
+    tee = compat_tee