Why doesn't this model use a new starting point for a time based find on every request?

Question

course.rb

  has_many :current_users, :through => :user_statuses, :source => :user, :conditions => ['user_statuses.updated_at > ?', 1.hour.ago]

console

Loading development environment (Rails 3.2.2)
>> course = Course.find(1)
  Course Load (0.3ms)  SELECT `courses`.* FROM `courses` WHERE `courses`.`id` = 1 LIMIT 1
=> #<Course id: 1, title: "Course 1", created_at: "2012-04-17 19:17:15", updated_at: "2012-04-17 19:17:15">
>> Time.now
=> 2012-04-23 08:29:45 -0400
>> course.current_users.count
   (0.4ms)  SELECT COUNT(*) FROM `users` INNER JOIN `user_statuses` ON `users`.`id` = `user_statuses`.`user_id` WHERE `user_statuses`.`user_id` = 1 AND (user_statuses.updated_at > '2012-04-23 12:28:40')
=> 0
>> Time.now
=> 2012-04-23 08:30:07 -0400
>> course.current_users.count
   (0.4ms)  SELECT COUNT(*) FROM `users` INNER JOIN `user_statuses` ON `users`.`id` = `user_statuses`.`user_id` WHERE `user_statuses`.`user_id` = 1 AND (user_statuses.updated_at > '2012-04-23 12:28:40')
=> 0
>>

Notice when checking the 1.hour.ago condition it uses the same time as a starting point despite the 30 second difference between the times when I made the request. Exiting console and restarting it clears it out, but it happens again with a new time. This behavior exists in testing and a browser as well. How do I get a model to use a time based condition for a has_many :through find?

score 2 · Answer 1 · edited May 23 '17 at 12:21

2

I believe you want to use a dynamic condition on your models relation.

Have a look at this SO question

Basically when your model loads, 1.hour.ago is evaluated only once. If I understand your question, you want it to be evaluated on each request.

Something like this (rails 3.1+) :

:conditions => lambda { |course| "user_statuses.updated_at > '#{1.hour.ago}'" }

edited May 23 '17 at 12:21

Community

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1

answered Apr 23 '12 at 12:46

Kyle

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I knew it was loading starting point time when it loaded the model. When I try your solution I get `ArgumentError: wrong number of arguments (1 for 0)` – Preacher Apr 23 '12 at 12:54
Which version of rails are you running? – Kyle Apr 23 '12 at 13:03
rails 3.2.2 (ruby 1.9.3-p125) – Preacher Apr 23 '12 at 13:06
@Preacher I edited the answer. The lambda needs one argument. You should be good now. – Kyle Apr 23 '12 at 13:14
I figured that, but I was getting a MySQL error, that I just solved. Just put some single quotes around `#{1.hour.ago}`, and you have an answer. – Preacher Apr 23 '12 at 13:30
Crap. Actually, passing an argument locks the time to when the model loads, just like my original code. – Preacher Apr 23 '12 at 13:45
Have a look at the link I provided. There are some other ideas there. – Kyle Apr 24 '12 at 02:35

score 0 · Accepted Answer · answered May 08 '12 at 16:31

Putting the query in the model at all didn't work, either in a has_many :through setup or in a method. So I ended up removing the association and putting the query in the controller. This allows the current time to be calculated when the request is made.

model:

has_many :user_statuses

controller:

@course = Course.find(params[:id])
@current_users = @course.user_statuses.where('updated_at > ?', 1.hour.ago)

Why doesn't this model use a new starting point for a time based find on every request?

2 Answers2