From: RichardOnRails <RichardDummyMailbox58407@...>
Date: 2010-12-23T23:10:16+09:00
Subject: Re: How to DRY code to prompt for parameters

On Dec 22, 11:55 pm, Josh Cheek <josh.ch...@gmail.com> wrote:
> [Note:  parts of this message were removed to make it a legal post.]
>
> On Wed, Dec 22, 2010 at 10:10 PM, RichardOnRails <
>
>
>
> RichardDummyMailbox58...@uscomputergurus.com> wrote:
> > I pasted code to prompt for a couple of parameter-values at
> >http://www.pastie.org/1399710.
>
> > Running this code under SciTE produces, for example:
> > Getting parms
> >        Account Number: 123
> >        Report  Period: 456
> > Showing parms
> >        @acct_num = 123
> >        @acct_period = 456
>
> > It is excessively verbose because I couldn't figure out how to use
> > meta-language to specify the parameter target names.  That led me to
> > using case statements to accept input values and then populate the
> > instance variables.
>
> > Can anyone suggest how I can use the instance variables as targets in
> > lieu of the case statements?  BTW, I want to get this working with
> > meta-programming.  I don't want to use some other approach, such as a
> > plug-in for getting arguments.
>
> > Thanks in Advance,
> > Richard
>
> I think you are looking for instance_variable_set and instance_variable_get.
> I don't really understand all the decisions you made, such as the array of
> hashes, to me that implies you want ordered hashes, but are on 1.8 (If you
> are in Rails, you have ActiveSupport loaded, and it provides an OrderedHash
> class that you can use) since they are ordered in 1.9. To get around that, I
> just made it an Array of Structs. Anyway, hopefully you can get out of this
> whatever you're trying to do.
>
> class X
>
>   def initialize
>     param = Struct.new :human_readable , :ivar
>     @rpt_parms = [
>       param.new( "Account Number" , "@acct_num"    ),
>       param.new( "Report  Period" , "@acct_period" ),
>     ]
>   end
>
>   def get_parms
>     @rpt_parms.each do |param|
>       print "\t#{param.human_readable}: "
>       instance_variable_set( param.ivar , gets.to_i ) # don't need to chomp,
> to_i will ignore the newline
>     end
>   end
>
>   def show_parms
>     @rpt_parms.each do |param|
>       value = instance_variable_get(param.ivar)
>       puts "\t#{param.human_readable} = #{value}"
>     end
>   end
>
>   def run
>     puts "Getting parms"
>     get_parms
>     puts "Showing parms"
>     show_parms
>   end
>
> end
>
> X.new.run

> I think you are looking for instance_variable_set and instance_variable_get.
That's also exactly the thing I needed!  Excellent!!

> To get around that, I just made it an Array of Structs.
Another responder did what I really wanted but was too stupid to do
is:
  @parms = {  "Account Name" => :acct_name,
              "Account Number" => :acct_num
           }   # etc.

Thanks very much for your insights.
Best wishes,
Richard