From: 7stud -- <dolgun@...>
Date: 2007-10-09T01:46:25+09:00
Subject: Re: optparse and required switches

Roger Nordqvist wrote:
> Hi ...
> 
> Im lost with optparse.
> 
> Got a couple of questions if its OK.
> 
> 1. I've been reading the documentation but I cant get it into my thick
> head how I tell an option that it is required or optional? I guess all
> opts are optional initially, but how do I say that an option is
> required.
> 
> 2. How do I gracefully tell the user that an option they provided is
> non-existent. I dont want ruby to crash with a big bang and a lot of
> error output.
> 
> At at last I would like to appologies if this are noobish questions. Im
> new to ruby and Im struggling to get a hang of it. But I dont read ruby
> code flawlessly and I dont always get the examples that the gems provide
> me.
> 


Try something like this:

require 'optparse'

opts = OptionParser.new do |opts|

  #value for option is required:
  opts.on("-t=ARG") do |val|
    puts "-t option entered with value=#{val}"
  end

  #value for option is optional:
  opts.on("-y [=RANDOM_CHARS]") do |val|
    puts "-y option entered with value=#{val}"
  end

end

begin
  #option -t is required:
  #----------------------
  found_opt_t = false

  ARGV.each do |word|
    if word[0, 2] == '-t'
      found_opt_t = true
    end
  end

  if not found_opt_t
    puts "Option -t is required.  Exiting..."
    exit
  end
  #----------------------

  opts.parse!(ARGV)

rescue OptionParser::MissingArgument => e
  puts e.to_str.capitalize.gsub("argument:", "value for:")
  puts "That option requires a value.  Please try again."
  puts "Exiting.."
  exit
end


Test run:

$ ruby r8test.rb -t 10 -y 15
-t option entered with value=10
-y option entered with value=15

$ ruby r8test.rb -t10
-t option entered with value=10

$ ruby r8test.rb -t
Missing value for: -t
That option requires a value.  Please try again.
Exiting..

$ ruby r8test.rb
Option -t is required.
Exiting...

$

-- 
Posted via http://www.ruby-forum.com/.