DecimalField now stores as float not string (#289)

tests/migration/decimalfield_as_float.py

@@ -0,0 +1,50 @@
+ # -*- coding: utf-8 -*-
+import unittest
+import decimal
+from decimal import Decimal
+
+from mongoengine import Document, connect
+from mongoengine.connection import get_db
+from mongoengine.fields import StringField, DecimalField, ListField
+
+__all__ = ('ConvertDecimalField', )
+
+
+class ConvertDecimalField(unittest.TestCase):
+
+    def setUp(self):
+        connect(db='mongoenginetest')
+        self.db = get_db()
+
+    def test_how_to_convert_decimal_fields(self):
+        """Demonstrates migrating from 0.7 to 0.8
+        """
+
+        # 1. Old definition - using dbrefs
+        class Person(Document):
+            name = StringField()
+            money = DecimalField(force_string=True)
+            monies = ListField(DecimalField(force_string=True))
+
+        Person.drop_collection()
+        Person(name="Wilson Jr", money=Decimal("2.50"),
+               monies=[Decimal("2.10"), Decimal("5.00")]).save()
+
+        # 2. Start the migration by changing the schema
+        # Change DecimalField - add precision and rounding settings
+        class Person(Document):
+            name = StringField()
+            money = DecimalField(precision=2, rounding=decimal.ROUND_HALF_UP)
+            monies = ListField(DecimalField(precision=2,
+                                            rounding=decimal.ROUND_HALF_UP))
+
+        # 3. Loop all the objects and mark parent as changed
+        for p in Person.objects:
+            p._mark_as_changed('money')
+            p._mark_as_changed('monies')
+            p.save()
+
+        # 4. Confirmation of the fix!
+        wilson = Person.objects(name="Wilson Jr").as_pymongo()[0]
+        self.assertTrue(isinstance(wilson['money'], float))
+        self.assertTrue(all([isinstance(m, float) for m in wilson['monies']]))