Rails - Sep 2013 - Retrieve duration (in string format) from database and convert to Ruby syntax for calculation

If I store 1.month as a string in the database, how do I convert
"1.month"
into 1.month?

This way I can use the "1.month" value stored in database to perform
the
following calculation.

Time.now + 1.month 

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I don''t think this is good idea. 1.month.to_i will return in seconds 
as 2592000. you can store this and while fetching you can use it as it is
Time.now + 2592000

On Friday, 20 September 2013 03:30:16 UTC-4, Fai Wong
wrote:
>
> If I store 1.month as a string in the database, how do I convert
"1.month"
> into 1.month?
>
> This way I can use the "1.month" value stored in database to
perform the
> following calculation.
>
> Time.now + 1.month 
>
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btw you can do it using "eval" like eval("1.month")

On Friday, 20 September 2013 03:30:16 UTC-4, Fai Wong
wrote:
>
> If I store 1.month as a string in the database, how do I convert
"1.month"
> into 1.month?
>
> This way I can use the "1.month" value stored in database to
perform the
> following calculation.
>
> Time.now + 1.month 
>
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Take a look at this gem: https://github.com/peleteiro/ruby-duration
—it will convert an arbitrary duration (like 1 month, 2 weeks, etc.) into 
seconds which can be stored in the DB. It is very similar to what Raj is 
recommending, just a little more formal. Either way you can avoid
eval''ing
code, and your calculation can be a lot more flexible.

On Friday, September 20, 2013 12:30:16 AM UTC-7, Fai Wong
wrote:
>
> If I store 1.month as a string in the database, how do I convert
"1.month"
> into 1.month?
>
> This way I can use the "1.month" value stored in database to
perform the
> following calculation.
>
> Time.now + 1.month 
>
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But not all months are 2592000 seconds long.....some are shorter and 
some are longer....
If you have a Date of 1 Jan and add 1.month to it you will get 1 Feb 
which is 31 days later.  If you have 1 Feb and you add 1.month you will 
get 1 Mar which is 28 or 29 days later.

You could just store the value as x so you could do Time.now + x.month

Norm

On 09/20/2013 01:47 AM, Raj Kumar wrote:
> I don''t think this is good idea. 1.month.to_i will return in
seconds
> as 2592000. you can store this and while fetching you can use it as it is
> Time.now + 2592000
>
> On Friday, 20 September 2013 03:30:16 UTC-4, Fai Wong wrote:
>
>     If I store 1.month as a string in the database, how do I convert
>     "1.month" into 1.month?
>
>     This way I can use the "1.month" value stored in database to
>     perform the following calculation.
>
>     Time.now + 1.month
>
> -- 
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On 20 September 2013 08:30, Fai Wong
<wongwf82-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> If I store 1.month as a string in the database, how do I convert
"1.month"
> into 1.month?
>
> This way I can use the "1.month" value stored in database to
perform the
> following calculation.
>
> Time.now + 1.month
If you really feel you need to do this then you can store "1.month" as
a string and use eval

1.9.3p194 :007 > delta = "1.month"
 => "1.month"
1.9.3p194 :008 > Time.now
 => 2013-09-22 08:52:13 +0100
1.9.3p194 :009 > Time.now + eval( delta )
 => 2013-10-22 08:52:23 +0100

However if you do this be /very/ careful about what can get into the
database as arbitrary code can be executed using eval and conceivably
your machine could be hacked.  I DO NOT recommend that you do this.
If your requirement is for a delta with values such as 1 month 3 weeks
and so on, then I suggest having two fields, one for the quantity and
an enumerated value for the period (month, week and so on).  Then work
it out in code.  Less efficient but /much/ safer.

Colin
>
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Thanks for your help everyone.

I ended up using Chronic Duration gem.

https://github.com/hpoydar/chronic_duration


On Sunday, September 22, 2013 3:58:58 PM UTC+8, Colin Law
wrote:
>
> On 20 September 2013 08:30, Fai Wong
<wong...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org <javascript:>>
> wrote: 
> > If I store 1.month as a string in the database, how do I convert 
> "1.month" 
> > into 1.month? 
> > 
> > This way I can use the "1.month" value stored in database to
perform the
> > following calculation. 
> > 
> > Time.now + 1.month 
>
> If you really feel you need to do this then you can store
"1.month" as
> a string and use eval 
>
> 1.9.3p194 :007 > delta = "1.month" 
>  => "1.month" 
> 1.9.3p194 :008 > Time.now 
>  => 2013-09-22 08:52:13 +0100 
> 1.9.3p194 :009 > Time.now + eval( delta ) 
>  => 2013-10-22 08:52:23 +0100 
>
> However if you do this be /very/ careful about what can get into the 
> database as arbitrary code can be executed using eval and conceivably 
> your machine could be hacked.  I DO NOT recommend that you do this. 
> If your requirement is for a delta with values such as 1 month 3 weeks 
> and so on, then I suggest having two fields, one for the quantity and 
> an enumerated value for the period (month, week and so on).  Then work 
> it out in code.  Less efficient but /much/ safer. 
>
> Colin 
>
> > 
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<javascript:>.
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>
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> > 
>
https://groups.google.com/d/msgid/rubyonrails-talk/a19f9925-f725-4cd5-9dfd-6c8c4b897bd6%40googlegroups.com.
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>
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