How do you specify a required switch (not argument) with Ruby OptionParser?

Question

I\'m writing a script and I want to require a --host switch with value, but if the --host switch isn\'t specified, I want the option parsing to fai

Answer 1

The idea is to define an OptionParser, then parse! it, and puts it if some fields are missing. Setting filename to empty string by default is probably not the best way to go, but you got the idea.

require 'optparse'

filename = ''
options = OptionParser.new do |opts|
    opts.banner = "Usage: swift-code-style.rb [options]"

    opts.on("-iNAME", "--input-filename=NAME", "Input filename") do |name|
        filename = name
    end
    opts.on("-h", "--help", "Prints this help") do
        puts opts
        exit
    end
end

options.parse!

if filename == ''
    puts "Missing filename.\n---\n"
    puts options
    exit
end

puts "Processing '#{filename}'..."

If -i filename is missing, it displays:

~/prj/gem/swift-code-kit ./swift-code-style.rb
Missing filename.
---
Usage: swift-code-style.rb [options]
    -i, --input-filename=NAME        Input filename
    -h, --help                       Prints this help