This little project tries to add a handful of convenient methods to Module, which make working with argument hashes in Ruby a bit easier.

• This only works with Ruby 1.9. This, however, is as far as I know no big problem because there is also a gem for Ruby 1.8...

# gem install keyword_arguments

(the gem can be found both on github and rubyforge)

require 'keyword_arguments'

class Test
  default_arguments {{a: 1, b: 2, c: 3}}
  def laissez_faire(args = {})
    args
  end

  required_arguments :a, :b
  def strict(args = { })
    args
  end

  required_arguments :a, :b
  allowed_arguments  :a, :b
  def even_stricter(args = { })
    args
  end
end

t = Test.new
t.laissez_faire                  # => {:a=>1, :b=>2, :c=>3}
t.laissez_faire a: 4, d: 5       # => {:a=>4, :b=>2, :c=>3, :d=>5}

t.strict a: 1, b: 2              # => {:a=>1, :b=>2}
t.strict                         # ~> -:26:in `<main>': Missing arguments: a, b (ArgumentError)

t.even_stricter a: 1, b: 2       # => {:a=>1, :b=>2}
t.even_stricter a: 1, b: 2, c: 3 # ~> -:29:in `<main>': Unknown arguments: c (ArgumentError)

Of course you can combine all of the three different methods (default_arguments, required_arguments and allowed_arguments)

This also works with methods on singleton classes ("class methods"), modules and included modules.

• You shouldn't redefine any of the *_arguments methods (as in

  class Test; def self.default_arguments; nil; end; end
  

  because then you won't be able to use the ones from our package unless you use ::Module.default_arguments

• default arguments are to be passed as blocks returning hashes.