From: Josh Cheek <josh.cheek@...>
Date: 2010-12-23T13:55:09+09:00
Subject: Re: How to DRY code to prompt for parameters

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On Wed, Dec 22, 2010 at 10:10 PM, RichardOnRails <
RichardDummyMailbox58407@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

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