From: Logan Capaldo <logancapaldo@...>
Date: 2007-05-07T03:53:12+09:00
Subject: Re: dynamically named variables or Constants

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On 5/6/07, Tom V. <ruby-talk@hinv.org> wrote:
>
> "Logan Capaldo" <logancapaldo@gmail.com> wrote:
> >
> > You guess is in the territory, but it's not really about session's
> > capability. if xyz_method is a controller action for instance, and
> > abc_method is a controller action, there's nothing guaranteeing per se
> > that you're state is going to be persisted between user interactions
> > with the web app. What you really need to store in session is the name
> > of the constant, AND it's value. and then you need to const_set it at
> > the beginning of every method where you make use of this live tree
> > thing.
> >
>
> Hi,
> Creating a new constant from session data still doesn't work.
> As you said I now store both constant_name and constant_value in session.
>
> However, when trying to test the new Constant (const_defined?),
> I get a NameError (see below).
>
> Also, when printing it, its value is printed, not its name:
> "{@new_constant}" --> "/path/to/nirvana".
> How do I access its name?
>
> Maybe you find an error in code.
> Or maybe you know of another way
> to create dynamically named variables..?
>
>
> class AbcController < ApplicationController
>
>   before_filter :get_constants, :except => :define_constants
>
>   def define_constants
>     @user = "tom"
>     constant_name = "#{@user.upcase}_PATH"
>     logger.info("#{constant_name}")
>     # output: TOM_PATH
>
>     constant_value = self::class::const_set(constant_name,
> "/path/to/nirvana")
>     logger.info("#{constant_value}")
>     # output: /path/to/nirvana
>
>     session[:constant_name] = constant_name
>     session[:constant_value] = constant_value
>   end
>
>   def get_constants
>     if session[:constant_name]
>       @constant_name = session[:constant_name]
>       logger.info("#{@constant_name}")
>       # output: TOM_PATH
>
>       if session[:constant_value]
>         @constant_value = session[:constant_value]
>         logger.info("#{@constant_value}")
>         # output: /path/to/nirvana
>
>         @new_constant = self::class::const_set(@constant_name,
> @constant_value)
>         logger.info("#{@new_constant}")
>         # output: /path/to/nirvana
>
>         evaluate_constant = self::class::const_defined?(@new_constant)

should be self::class:const_defined?(@constant_name) of course.
@new_constant is gonna hold the value of the constant, not the name.


        # output: NameError (wrong constant name /path/to/nirvana)
>
>       end
>     end
>   end
>
> end
>
> Thanks for your input,
> Tom.
>
>

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