fix issue "TypeError: 'int' object is not iterable" during update (pre_save), add tests (#100)

example/app/fixtures/app_data.json

@@ -6,7 +6,8 @@
         "title": "My book 1",
         "tags": "sex,work,happy",
         "categories": "1,3,5",
-        "published_in": "BC,AL,AK"
+        "published_in": "BC,AL,AK",
+        "chapters": "1"
     }
 },
 {

example/app/migrations/0001_initial.py

@@ -1,6 +1,4 @@
-# -*- coding: utf-8 -*-
-# Generated by Django 1.9 on 2016-09-22 20:34
-from __future__ import unicode_literals
+# Generated by Django 2.2.6 on 2019-10-31 08:31
 
 from django.db import migrations, models
 import multiselectfield.db.fields
@@ -22,6 +20,7 @@ class Migration(migrations.Migration):
                 ('categories', multiselectfield.db.fields.MultiSelectField(choices=[(1, 'Handbooks and manuals by discipline'), (2, 'Business books'), (3, 'Books of literary criticism'), (4, 'Books about literary theory'), (5, 'Books about literature')], default=1, max_length=9)),
                 ('tags', multiselectfield.db.fields.MultiSelectField(blank=True, choices=[('sex', 'Sex'), ('work', 'Work'), ('happy', 'Happy'), ('food', 'Food'), ('field', 'Field'), ('boring', 'Boring'), ('interesting', 'Interesting'), ('huge', 'Huge'), ('nice', 'Nice')], max_length=54, null=True)),
                 ('published_in', multiselectfield.db.fields.MultiSelectField(choices=[('Canada - Provinces', (('AB', 'Alberta'), ('BC', 'British Columbia'))), ('USA - States', (('AK', 'Alaska'), ('AL', 'Alabama'), ('AZ', 'Arizona')))], max_length=2, verbose_name='Province or State')),
+                ('chapters', multiselectfield.db.fields.MultiSelectField(choices=[(1, 'Chapter I'), (2, 'Chapter II')], default=1, max_length=3)),
             ],
         ),
     ]

example/app/models.py

@@ -27,6 +27,13 @@ CATEGORY_CHOICES = (
     (5, _('Books about literature')),
 )
 
+ONE = 1
+TWO = 2
+CHAPTER_CHOICES = (
+    (ONE, 'Chapter I'),
+    (TWO, 'Chapter II')
+)
+
 TAGS_CHOICES = (
     ('sex',         _('Sex')),          # noqa: E241
     ('work',        _('Work')),         # noqa: E241
@@ -67,6 +74,7 @@ class Book(models.Model):
     published_in = MultiSelectField(_("Province or State"),
                                     choices=PROVINCES_AND_STATES,
                                     max_choices=2)
+    chapters = MultiSelectField(choices=CHAPTER_CHOICES, default=ONE)
 
     def __str__(self):
         return self.title

example/app/test_msf.py

@@ -23,8 +23,7 @@ from django.test import TestCase
 
 from multiselectfield.utils import get_max_length
 
-from .models import Book, PROVINCES, STATES, PROVINCES_AND_STATES
-
+from .models import Book, PROVINCES, STATES, PROVINCES_AND_STATES, ONE, TWO
 
 if sys.version_info < (3,):
     u = unicode  # noqa: F821
@@ -92,6 +91,27 @@ class MultiSelectTestCase(TestCase):
         if form.is_valid():
             form.save()
 
+    def test_empty_update(self):
+        book = Book.objects.get(id=1)
+        self.assertEqual(book.get_chapters_list(), ["Chapter I"])
+        book.chapters = {}
+        book.save(update_fields=['chapters'])
+        self.assertTrue(len(book.chapters) == 0)
+
+    def test_single_update(self):
+        book = Book.objects.get(id=1)
+        self.assertEqual(book.get_chapters_list(), ["Chapter I"])
+        book.chapters = {ONE}
+        book.save(update_fields=['chapters'])
+        self.assertEqual(book.get_chapters_list(), ["Chapter I"])
+
+    def test_multiple_update(self):
+        book = Book.objects.get(id=1)
+        self.assertEqual(book.get_chapters_list(), ["Chapter I"])
+        book.chapters = {ONE, TWO}
+        book.save(update_fields=['chapters'])
+        self.assertEqual(book.get_chapters_list(), ["Chapter I", "Chapter II"])
+
     def test_object(self):
         book = Book.objects.get(id=1)
         self.assertEqual(book.get_tags_display(), 'Sex, Work, Happy')

multiselectfield/db/fields.py

@@ -138,7 +138,7 @@ class MultiSelectField(models.CharField):
         return MultiSelectFormField(**defaults)
 
     def get_prep_value(self, value):
-        return '' if value is None else ",".join(value)
+        return '' if value is None else ",".join(map(str, value))
 
     def get_db_prep_value(self, value, connection, prepared=False):
         if not prepared and not isinstance(value, string_type):
@@ -149,7 +149,12 @@ class MultiSelectField(models.CharField):
         choices = dict(self.flatchoices)
 
         if value:
-            return value if isinstance(value, list) else MSFList(choices, value.split(','))
+            if isinstance(value, list):
+                return value
+            elif isinstance(value, string_type):
+                return MSFList(choices, value.split(','))
+            elif isinstance(value, (set, dict)):
+                return MSFList(choices, list(value))
         return MSFList(choices, [])
 
     if VERSION < (2, ):