Rails 4 Comparing Datetime in API

Question

Hi I am having issues comparing datetimes with a Rails 4 JSON API.

I use a scope with the created_at attribute

scope :later_than, -> (date) { where('created_at > ?', date) }

The JSON returned for the created_at looks like

"created_at" = "2015-05-07T01:16:43.611Z"

When sending this same datetime the API log and SQL look like

Parameters: {"later_than"=>"2015-05-06T21:16:43.611-0400"}

created_at > '2015-05-06T21:16:43.611-0400'

In the console

Object.first.created_at
=> Thu, 07 May 2015 01:16:43 UTC +00:00
Object.first.created_at > '2015-05-06T21:16:43.611-0400'
=> true

The last comparison should be false, but instead it is true and the scope is not working properly.

When logging

Object.first.created_at - '2015-05-06T21:16:43.611-0400'.to_datetime
=> 0.000402

So what happens is:

• the API returns datetime truncated to milliseconds
• Rails compares datetimes with microseconds precision

Thus when sending the same datetime to the API, the microseconds will be set to 0 and thus the comparison is not going to work as expected.

Is there a way to tell Rails: compare datetimes with millisecond precision?

Answer 1

Is Message.first.created_at equal to Thu, 07 May 2015 01:16:43 UTC +00:00 ? (you have Object.first.created_at up there) because if it is, the console expression is behaving correctly and should be true.

Answer 2

你尝试过这样的事情吗？

Object.first.created_at > Time.parse('2015-05-06T21:16:43.611-0400')