things.rb

module Things
  class Thing
    instance_methods.each { |m| undef_method m unless m =~ /^__/ or ['instance_eval'].include?(m) }
    include Things

    def initialize
      @hash = {}
    end

    def __hash
      @hash
    end

    def method_missing meth, *args, &block
      if meth.to_s =~ /^(.+)=$/
        @hash[$1.to_sym] = args.first
      else
        if block
          @hash[meth] = thing &block
        else
          @hash[meth] = args.first if args.first
          @hash[meth]
        end
      end
    end
  end

  def thing &block
    thing = Thing.new
    thing.instance_eval &block if block_given?
    thing
  end
end

things_spec.rb

require File.dirname(__FILE__)+'/spec_helper'
require 'things'

describe "a thing" do
  include Things

  it "should initially return nil for any method" do
    thing.qwerty.should be_nil
  end

  it "should allow arbitrary values to be assigned with setter" do
    t = thing
    t.qwerty = 4
    t.qwerty.should == 4
  end

  it "should allow arbitrary values to be assigned with method call" do
    t = thing
    t.qwerty 4
    t.qwerty.should == 4
  end

  it "should allow arbitrary values to be assigned in thing block" do
    t = thing {
      qwerty 4
    }
    t.qwerty.should == 4
  end

  it "should allow nested things to be assigned by using thing method" do
    t = thing {
      qwerty __thing {
        asdf 4
      }
    }
    t.qwerty.asdf.should == 4
  end

  it "should allow nested things to be assigned by passing block" do
    t = thing {
      qwerty {
        asdf 4
      }
    }
    t.qwerty.asdf.should == 4
  end

  it "should expose hash so it is possible to find out about things" do
    t = thing {
      qwerty {
        asdf 4
      }
    }
    t.__hash.keys.should == [:qwerty]
    t.qwerty.__hash.keys.should == [:asdf]
  end

  it "should handle references in block" do
    q = thing {
      asdf 4
    }
    t = thing {
      q2 = qwerty q
      qwerty2 q2
    }
    t.qwerty.asdf.should == 4
    t.qwerty2.asdf.should == 4
  end
end