From: Frederick Cheung <frederick.cheung@...>
Date: 2008-08-11T18:50:35+09:00
Subject: Re: Expanding variables in a string


On 11 Aug 2008, at 06:02, Heesob Park wrote:

> 2008/8/11 Thind, Aman <aman.thind@lehman.com>:
>> Thanks for the reply!
>>
>> If I do eval(myaction) then it thinks all the words in the string are
>> variables and complains:
>>
>> irb(main):002:0> myaction = 'perl #{ENV[HOME_SCRIPTS]}/myscript.pl
>> -#{params[:date]}'
>> => "perl \#{ENV[HOME_SCRIPTS]}/myscript.pl -\#{params[:date]}"
>>
>> irb(main):004:0> eval myaction
>> NameError: undefined local variable or method `perl' for main:Object
>>
>> What I want is for all the known variables in the string to be  
>> expanded;
>> the same effect that assignment with double quotes has.
>>
>> Please remember I know using double quotes in the assignment to  
>> myaction
>> would solve the problem but I am doing this assignment only for
>> illustration.
>>
>> I actually get the string from a db query so have to expand the
>> variables after the assignment.
>>
> You could try something like this:
>
> myaction.gsub(/#\{(.+?)\}/){eval($1)}

Or even
my_interpolated_action = eval "%@#{action.gsub('@','\@')}@"
(lifted from activerecord where something similar is done)

Fred