Rails - Oct 2010 - Rails 2.3.8 - What happens to a datetime field between a form being submitted and the controller receiving the params

I currently have a model that simply contains one datetime field:

class CreateElectricityReadings < ActiveRecord::Migration
  def self.up
    create_table :clocks do |t|
      t.datetime :time_keeper
      t.timestamps
    end
  end

  def self.down
    drop_table :clocks
  end
end

If I enter the date string "13/10/2010" into this field its showing up
in the controller as params[:clock][:time_keeper] "2010-10-13 23:00:00
UTC".  I''ve tried overloading
ActiveRecord::ConnectionAdapters::Column string_to_date(string) and
ActiveRecord::ConnectionAdapters::Column string_to_time(string) but
these seems to get hit when an object is saved not between the form
submitting and the controller receiving the params object.  Where is
the mysterious 23:00:00 hours coming from?  Can anyone point me to a
good piece of reference reading for how dates and times work in rails
land?

Thanks

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voidstar wrote in post #949920:
> I currently have a model that simply contains one datetime field:
>
> class CreateElectricityReadings < ActiveRecord::Migration
>   def self.up
>     create_table :clocks do |t|
>       t.datetime :time_keeper
>       t.timestamps
>     end
>   end
>
>   def self.down
>     drop_table :clocks
>   end
> end
>
> If I enter the date string "13/10/2010" into this field its
showing up
> in the controller as params[:clock][:time_keeper] "2010-10-13 23:00:00
> UTC".
Then you just need to call to_s on the date with the format you want. 
Do this in the controller or the view: it''s just like any other 
presentation issue.  Dates are not stored as strings in the DB.
>  I''ve tried overloading
> ActiveRecord::ConnectionAdapters::Column string_to_date(string) and
> ActiveRecord::ConnectionAdapters::Column string_to_time(string) but
> these seems to get hit when an object is saved not between the form
> submitting and the controller receiving the params object.  Where is
> the mysterious 23:00:00 hours coming from?
If I had to guess, I''d guess that you''re in UTC+1 (Central
European
Time).  So perhaps it''s storing the time as 0:00 local time, then 
converting to UTC.  But I could be wrong.
>  Can anyone point me to a
> good piece of reference reading for how dates and times work in rails
> land?
You''re overthinking it.  Rails does some conversion when the form is 
submitted to convert three form fields (day, month, year) into a Date 
object for the DB, and then saves it to a date or datetime field in the 
DB.  In this case, you specified a datetime field in your migration, so 
when Rails retrieves the record, it puts the value into a DateTime 
object.  If you don''t want the time, don''t use a datetime
field in the
DB -- or just ignore the time.
>
> Thanks
Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org

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Hey,
Thanks for the reply, I could easily write some code to discard the
time field, which is what I''ll probably do now but I''d just
like to
know how rails is doing this, I guess is should go about downloading
the rails source and grok it myself.

I''m in GMT but using daylight savings.

I guess if I just reset the time members of the DateTime object its
returning to me I''m relatively insulated from errors if this
translation changes in a future release.

Thanks
Barry

On Oct 13, 7:20 pm, Marnen Laibow-Koser
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> voidstar wrote in post #949920:
>
>
>
>
>
> > I currently have a model that simply contains one datetime field:
>
> > class CreateElectricityReadings < ActiveRecord::Migration
> >   def self.up
> >     create_table :clocks do |t|
> >       t.datetime :time_keeper
> >       t.timestamps
> >     end
> >   end
>
> >   def self.down
> >     drop_table :clocks
> >   end
> > end
>
> > If I enter the date string "13/10/2010" into this field its
showing up
> > in the controller as params[:clock][:time_keeper] "2010-10-13
23:00:00
> > UTC".
>
> Then you just need to call to_s on the date with the format you want.
> Do this in the controller or the view: it''s just like any other
> presentation issue.  Dates are not stored as strings in the DB.
>
> >  I''ve tried overloading
> > ActiveRecord::ConnectionAdapters::Column string_to_date(string) and
> > ActiveRecord::ConnectionAdapters::Column string_to_time(string) but
> > these seems to get hit when an object is saved not between the form
> > submitting and the controller receiving the params object.  Where is
> > the mysterious 23:00:00 hours coming from?
>
> If I had to guess, I''d guess that you''re in UTC+1
(Central European
> Time).  So perhaps it''s storing the time as 0:00 local time, then
> converting to UTC.  But I could be wrong.
>
> >  Can anyone point me to a
> > good piece of reference reading for how dates and times work in rails
> > land?
>
> You''re overthinking it.  Rails does some conversion when the form
is
> submitted to convert three form fields (day, month, year) into a Date
> object for the DB, and then saves it to a date or datetime field in the
> DB.  In this case, you specified a datetime field in your migration, so
> when Rails retrieves the record, it puts the value into a DateTime
> object.  If you don''t want the time, don''t use a datetime
field in the
> DB -- or just ignore the time.
>
>
>
> > Thanks
>
> Best,
> --
> Marnen Laibow-Koserhttp://www.marnen.org
> mar...-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
>
> --
> Posted viahttp://www.ruby-forum.com/.
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voidstar wrote in post #950126:
> Hey,
> Thanks for the reply, I could easily write some code to discard the
> time field, which is what I''ll probably do now
You don''t have to discard anything.  Just ignore it.

Check Rails'' field types; I think if you define the field in the 
migration as date instead of datetime, you will get a Date object from 
the DB, not the DateTime you currently have.
> but I''d just like to
> know how rails is doing this, I guess is should go about downloading
> the rails source and grok it myself.
You''ve already got the Rails source.
>
> I''m in GMT but using daylight savings.
>
> I guess if I just reset the time members of the DateTime object its
> returning to me I''m relatively insulated from errors if this
> translation changes in a future release.
There''s no need to reset.   There''s no translation, really;
Rails is
creating a DateTime object, so it needs a time value.  Again, you''re 
overthinking it and persuading yourself into more complex code than is 
actually necessary.
>
> Thanks
> Barry
Best,
-- 
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org

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I need a date/time object due to domain requirements although at this
point I don''t care about the time object, I just want it to be
midnight.  There are other ways for the user to enter data into this
table where the time element becomes relevant.

Where do I have the rails source?  Also do you know what file/class
handles receiving a post request from a form?

If anyone else is interested here''s the code I''m using to
reset the
time to midnight.

    @gas_reading = @user.gas_readings.build(params[:gas_reading])

    @gas_reading.start_date = @gas_reading.start_date.change(:hour =>
0, :min => 0, :second => 0) unless @gas_reading.start_date.nil?
    @gas_reading.end_date = @gas_reading.end_date.change(:hour =>
0, :min => 0, :second => 0) unless @gas_reading.end_date.nil?



On Oct 14, 1:34 pm, Marnen Laibow-Koser
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> voidstar wrote in post #950126:
>
> > Hey,
> > Thanks for the reply, I could easily write some code to discard the
> > time field, which is what I''ll probably do now
>
> You don''t have to discard anything.  Just ignore it.
>
> Check Rails'' field types; I think if you define the field in the
> migration as date instead of datetime, you will get a Date object from
> the DB, not the DateTime you currently have.
>
> > but I''d just like to
> > know how rails is doing this, I guess is should go about downloading
> > the rails source and grok it myself.
>
> You''ve already got the Rails source.
>
>
>
> > I''m in GMT but using daylight savings.
>
> > I guess if I just reset the time members of the DateTime object its
> > returning to me I''m relatively insulated from errors if this
> > translation changes in a future release.
>
> There''s no need to reset.   There''s no translation,
really; Rails is
> creating a DateTime object, so it needs a time value.  Again,
you''re
> overthinking it and persuading yourself into more complex code than is
> actually necessary.
>
>
>
> > Thanks
> > Barry
>
> Best,
> -- 
> Marnen Laibow-Koserhttp://www.marnen.org
> mar...-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
>
> --
> Posted viahttp://www.ruby-forum.com/.
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On 14 October 2010 15:52, voidstar
<barryodriscoll-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> If anyone else is interested here''s the code I''m using to
reset the
> time to midnight.
I''d suggest you use the Rails'' ".beginning_of_day"
method...

http://apidock.com/rails/ActiveSupport/CoreExtensions/Date/Calculations/beginning_of_day

... possibly easier and certainly more idiomatic.

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On Oct 14, 2010, at 10:52 AM, voidstar wrote:
> Where do I have the rails source?  Also do you know what file/class
> handles receiving a post request from a form?
Open a new Terminal window and type gem server [and press return].  
Open a new browser and visit http://0.0.0.0:8808

Each Gem you have installed will (probably) have two links next to its  
name, rdoc and www. The rdoc is whatever was generated when you  
installed the Gem, and the www will be whatever passes for the  
developer''s Web site.

Walter

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On 14 October 2010 15:52, voidstar
<barryodriscoll-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> I need a date/time object due to domain requirements although at this
> point I don''t care about the time object, I just want it to be
> midnight.  There are other ways for the user to enter data into this
> table where the time element becomes relevant.
My understanding of this issue (which may be flawed) is that if you
have a datetime field on a form the rails assumes the value entered is
in local time, and converts it to gmt ready to be put in the database.
 I _think_ that if, in environment.rb you put
config.time_zone = ''UTC''
then it will assume that the value entered is already in UTC and will
not apply the timezone offset.

Colin
>
> Where do I have the rails source?  Also do you know what file/class
> handles receiving a post request from a form?
>
> If anyone else is interested here''s the code I''m using to
reset the
> time to midnight.
>
>    @gas_reading = @user.gas_readings.build(params[:gas_reading])
>
>    @gas_reading.start_date = @gas_reading.start_date.change(:hour =>
> 0, :min => 0, :second => 0) unless @gas_reading.start_date.nil?
>    @gas_reading.end_date = @gas_reading.end_date.change(:hour =>
> 0, :min => 0, :second => 0) unless @gas_reading.end_date.nil?
>
>
>
> On Oct 14, 1:34 pm, Marnen Laibow-Koser
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:
>> voidstar wrote in post #950126:
>>
>> > Hey,
>> > Thanks for the reply, I could easily write some code to discard
the
>> > time field, which is what I''ll probably do now
>>
>> You don''t have to discard anything.  Just ignore it.
>>
>> Check Rails'' field types; I think if you define the field in
the
>> migration as date instead of datetime, you will get a Date object from
>> the DB, not the DateTime you currently have.
>>
>> > but I''d just like to
>> > know how rails is doing this, I guess is should go about
downloading
>> > the rails source and grok it myself.
>>
>> You''ve already got the Rails source.
>>
>>
>>
>> > I''m in GMT but using daylight savings.
>>
>> > I guess if I just reset the time members of the DateTime object
its
>> > returning to me I''m relatively insulated from errors if
this
>> > translation changes in a future release.
>>
>> There''s no need to reset.   There''s no translation,
really; Rails is
>> creating a DateTime object, so it needs a time value.  Again,
you''re
>> overthinking it and persuading yourself into more complex code than is
>> actually necessary.
>>
>>
>>
>> > Thanks
>> > Barry
>>
>> Best,
>> --
>> Marnen Laibow-Koserhttp://www.marnen.org
>> mar...-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
>>
>> --
>> Posted viahttp://www.ruby-forum.com/.
>
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voidstar wrote in post #950166:
> I need a date/time object due to domain requirements although at this
> point I don''t care about the time object,
Huh?  Design for what you have now, not what you might need in future.

[...]
> Where do I have the rails source?
Do you really need to ask?  Remember, Ruby is an interpreted language. 
That means that you''ve got the source wherever the Rails gem is 
installed (in vendor/rails if you''ve done that, or wherever "gem
which
rails" tells you).

Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org

-- 
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Thanks for the replies,

beginning_of_day makes a lot more sense.

Yes Colin that''s what''s happening, I''d just like to
know where exactly
the string goes from "dd/mm/yyyy" to being "yyyy-mm-dd hh:mm:ss
timezone offset" and if there''s anyway for me to control/over ride
that behaviour.

Marnen, You''re right what we''re doing right now isn''t
good and we''re
creating technical debt.  As a team we''ve discussed this and given the
current requirements and priorities/time we have left, we''ve decided
to do it this way.

Also I wouldn''t have asked how to see the rails/ruby code if I knew
how.  I''m coming from java land and before that c++ where I''m
used to
having to grab the sources for libraries before being able to debug
them or read them.

The source seems to be scattered about in different gems on my
machine, I found doing a "git clone git://github.com/rails/rails.git
v2.3.8" was handier to have everything in one place.  Any suggestions
on where to start looking for how rails accepts a post request and
builds the params object and sends it to the correct controller?

Thanks again for all the help
Barry

On Oct 14, 5:15 pm, Marnen Laibow-Koser
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> voidstar wrote in post #950166:
>
> > I need a date/time object due to domain requirements although at this
> > point I don''t care about the time object,
>
> Huh?  Design for what you have now, not what you might need in future.
>
> [...]
>
> > Where do I have the rails source?
>
> Do you really need to ask?  Remember, Ruby is an interpreted language.
> That means that you''ve got the source wherever the Rails gem is
> installed (in vendor/rails if you''ve done that, or wherever
"gem which
> rails" tells you).
>
> Best,
> --
> Marnen Laibow-Koserhttp://www.marnen.org
> mar...-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
>
> --
> Posted viahttp://www.ruby-forum.com/.
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On 14 October 2010 19:38, voidstar
<barryodriscoll-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Thanks for the replies,
>
> beginning_of_day makes a lot more sense.
>
> Yes Colin that''s what''s happening, I''d just like
to know where exactly
> the string goes from "dd/mm/yyyy" to being "yyyy-mm-dd
hh:mm:ss
> timezone offset" and if there''s anyway for me to control/over
ride
> that behaviour.
Where and how _exactly_ are you seeing it as this string?  What do you
see in the log when the form is posted?
Apologies if you have already provided that info, I have not got time
to look back in detail at the thread at this moment.

Colin

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