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Accessing datetime via read_attribute loses timezone
Reported by Artem Ignatiev | December 26th, 2008 @ 02:43 PM | in 2.x
In my project I needed to alter getter method for datetime attribute, like that:
class SomeModel < ActiveRecord::Base
has_one :overriding_model
def start_time
if overriding_model
overriding_model.start_time
else
read_attribute(:start_time)
end
end
end
With such definition start_time method began to
return instances of Time class (with time in UTC timezone), so that
broke displaying of times for us.
Here's diff to test case that will fail test_time_attributes_are_retrieved_in_current_time_zone
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 77ee8d8..cc5198f 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -146,7 +146,9 @@ class AttributeMethodsTest < ActiveRecord::TestCase
record[:written_on] = utc_time
assert_equal utc_time, record.written_on # record.written on is equal to (i.e., simultaneous with) utc_time
assert_kind_of ActiveSupport::TimeWithZone, record.written_on # but is a TimeWithZone
+ assert_kind_of ActiveSupport::TimeWithZone, record.read_attribute(:written_on)
assert_equal ActiveSupport::TimeZone["Pacific Time (US & Canada)"], record.written_on.time_zone # and is in the current Time.zone
+ assert_equal ActiveSupport::TimeZone["Pacific Time (US & Canada)"], record.read_attribute(:written_on).time_zone
assert_equal Time.utc(2007, 12, 31, 16), record.written_on.time # and represents time values adjusted accordingly
end
end
Comments and changes to this ticket
-
-
Frederick Cheung December 26th, 2008 @ 10:26 PM
Well currently the conversion happens at the level of the automatically generated attribute reader so it's not surprising that this happens.
All you need to do is change your code to say
read_attribute(:start_time).in_time_zoneFurthermore I'm of the opinion that time zone conversions etc... are none of read_attribute's business. It's a low level method, so if you use it there will be slighly more faffing around
-
Artem Ignatiev December 29th, 2008 @ 12:07 PM
What version of Rails are you using? Using 2.2, patch is against 07298fd0929ae1c6dd6d1b41bf320112d6bfc6a0 (Fri Dec 26 01:49:14 2008 +0000)
2Frederick:
Well, after reading the source I came to conclusion that it's intended behaviour when reading datetime attributes.
Perhaps, a note should be added to rdoc about timezone conversion when reading/writing datetime attributes?
-
Geoff Buesing January 7th, 2009 @ 06:29 AM
- State changed from “new” to “wontfix”
In agreement with Frederick -- time zone conversions shouldn't be done inside of read_attribute.
@Artem, agreed, an rdoc note could help by explaining that time zone conversions are done via generated methods, and not inside of read_attribute.
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Artem Ignatiev