CLI with sub-commands using dynamic dispatch

metasyntactic_puns.rb

class PunCommands
  def self.foo
    puts "you could have fooed me"
  end

  def self.bar
    puts "guy walks into a bar"
  end

  def self.baz
    puts "bazically it works"
  end
end

defined_commands = PunCommands.methods - PunCommands.superclass.methods

unless ARGV.length == 1
  puts "requires one argument, the command you'd like to run"
  exit 1
end

input_command = ARGV.first.to_sym

if PunCommands.respond_to?(input_command)
  PunCommands.send(input_command)
  exit 0
else
  puts "no command by that name, try: #{defined_commands.join(', ')}"
  exit 1
end