Multiple Time.zone support

[Nerian]

Hi,

I am implementing reservation management now and I just noticed some weird behaviour when datatable is showing DateTime fields. The time (hours) part is showing correctly when the table is first initialised, but then when a filter is used the table actually shows times as if the timezone was UTC.

Which makes total sense since the Datatable Filter part is handled from a controller in EffectiveDatatable.

In my controllers this bit sets the Time.zone for the current account:

class ApplicationController < ActionController::Base
  around_action :set_time_zone, if: :current_account

  def set_time_zone
    Time.use_zone(current_account.time_zone) do
      yield
    end
  end

end

But that won't effect EffectiveDatatable::DatatablesController.

I was wondering how do you handle different time zones when using EffectiveDatatable.

Thanks

[Nerian]

An idea:

Use something similar to what you do in EffectiveDatatables.authorization_method.

If I could have a method that gets called before DatatablesController#Show then I can put my Time.zone handler there – this could potentially be used for something too.

[Nerian]

Actually I see that DatatablesController inherits from ApplicationController. So why wouldn't things just work O-o.

[matt-riemer]

Yea, great questions:

1.) Datatables doesn't do anything with timezones itself.

https://github.com/code-and-effect/effective_datatables/blob/master/app/models/effective/effective_datatable/format.rb#L82

2.) I do kind of enforce the %Y-%m-%d format so that the searching will work correctly. You can just type "2019-04" in a date filter box, and it'll pull all the April 2019 records.

3.) Rails and timezones suck. I generally use two approaches:

a.) I set my rails server config.time_zone to be "MST (Mountain Standard Time)" (that's the zone I'm in) so then all .strftime and date displays, are in that MST time zone.

b.) Some sites I need user specific time zone display. So I do something very similar to the controller code you posted above. This has the effect of displaying the time zone as per the configured value.

You could do something like:

around_action :set_time_zone, if: -> { params['controller'] == 'effective/datatables' && params['action'] == show }

if you wanted to only affect the datatatables action.

https://github.com/code-and-effect/effective_datatables/blob/master/app/controllers/effective/datatables_controller.rb

[matt-riemer]

You could also do a custom column maybe

col(:my_date) { |date| date.in_time_zone(current_user.time_zone).strftime('%F') }.

There might be some weird "I'm searching for "2019-04-05" but I'm getting records displayed as "2019-04-06" or some similar "off by time zone hours" with this approach

You could probably override the .search to use time zone too on just one column...

Imho that ApplicationController setting the time zone per request is the right approach. It'll work for datatables, and everything else on your page.

[Nerian]

Yup, I am using a custom column.

col :date, label: I18n.t('general.date') do |reservation|
  logger.debug Time.zone
  "#{l(reservation.date_start, format: :short)} <br> #{l(reservation.date_end, format: :short)}"
end

application..rb

class Application < Rails::Application
  config.time_zone = 'UTC' 
end

On the first render, the logger shows (GMT+01:00) Madrid. Which is correct for the user.

When I apply a filter, or order, or do anything that would call for the Datatable controller then it uses an incorrect zone: (GMT+00:00) UTC. Which is what I set as the application default

[Nerian]

I am going to use the demo app and see if I can reproduce this there.

[Nerian]

After 2 hour of debugging, and finally monkeypatching the zone=() method in ActiveSupport to see how that values were changing around, I noticed that Time.zone was not being set all when doing a remote operation with the table. And then I saw where the error was: Between the desk and screen.

This was the around filter that I had set:

around_action :set_time_zone, if: :current_account

That current_account is going to return nil when within the EffectiveDatatable Controller because it needs the account_id in the route. So the filter is not going to act and thereby Time.zone would not be set. And that explains it all.

😭 🔫

FUuuuuuuuuuuuuuck Oh blimey, what an unfortunate miss.

Thanks for your help!

[matt-riemer]

lol, been there done that!

Oooh man if I could have all the hours back that I spent on debugging my own code. :)