Datetime in Rails query using .select

Question

I have two rails models, MyParent and MyChild.

I'm trying to build a query using the rails .select() methods to efficiently extra a large number of rows for the database.

I want to pull back a number of columns from across the two tables, but when I reference a column which is of type datetime (or timestamp) but not in the original model, it is returned as a string.

Eg:

irb(main)> MyChild.select(['created_at as child_date', 'created_at']).first.child_date.class
=> String #Bad!!!
irb(main)> MyChild.select(['created_at as child_date', 'created_at']).first.created_at.class
=> ActiveSupport::TimeWithZone  #YAY!!!!

I first encountered this problem when attempted to pull a datetime from the MyParent table using joins().

How can I tell rails that I want child_date as a ActiveSupport::TimeWithZone object?

I'm using the latest version of Rails 3.2.

It already is a date though. The problem seems to be that Rails can't figure out how to convert the sql result without info from ActiveRecord. — ewalk
– ewalk, Commented May 7, 2013 at 19:14

ewalk · Accepted Answer · 2013-05-09 16:07:50Z

1

The only solution that I could come up with was to cast the resulting date back into a TimeWithZone object

Time.zone.parse(MyChild.select(['created_at as child_date']).first.child_date)
# returns a ActiveSupport::TimeWithZone object

answered May 9, 2013 at 16:07

ewalk

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