args.rb

class Thing
  def foo(first, bar: 123)
    __callee__ # => :foo
    __dir__ # => "/private/var/folders/gz/5xvm5fkx79bdr3bnbchj68980000gn/T/seeing_is_believing_temp_dir20140501-76590-1yme1ex"
    __id__ # => 70335328646640
    __method__ # => :foo
    binding # => #<Binding:0x007ff0708ee7d0>
    caller # => ["/var/folders/gz/5xvm5fkx79bdr3bnbchj68980000gn/T/seeing_is_believing_temp_dir20140501-76590-1yme1ex/program.rb:29:in `<main>'"]
    caller_locations # => ["/var/folders/gz/5xvm5fkx79bdr3bnbchj68980000gn/T/seeing_is_believing_temp_dir20140501-76590-1yme1ex/program.rb:29:in `<main>'"]
    local_variables # => [:first, :bar, :args]
    object_id # => 70335328646640

    method(__method__).arity # => 1
    method(__method__).parameters # => [[:req, :first], [:key, :bar]]
    method(__method__).name # => :foo
    method(__method__).name == __method__ # => true
    method(__method__).owner # => Thing
    method(__method__).receiver # => #<Thing:0x007ff0708eebe0>
    method(__method__).receiver == self # => true
    method(__method__).source_location # => ["/var/folders/gz/5xvm5fkx79bdr3bnbchj68980000gn/T/seeing_is_believing_temp_dir20140501-76590-1yme1ex/program.rb", 2]

    args = (local_variables - [:args]).inject({}) { |hash, name|
      hash[name] = instance_eval(name.to_s); hash
    }
    args # => {:first=>1, :bar=>123}
  end
end

Thing.new.foo 1