From: Ross Bamford <rosco@...>
Date: 2006-02-05T06:18:19+09:00
Subject: Re: Extract hash into local variables?

On Sat, 04 Feb 2006 19:46:03 -0000, csn <cool_screen_name90001@yahoo.com>  
wrote:

> def foo2(args = {:a=>1, :b=>2, :c=>3})
>   a,b,c = args.values
>
>   puts a,b,c
> end
>

Careful with that, I think hash order is undefined?

I was playing a bit with this stuff recently and came up with this:

	class Method
	  def arg_names
	    catch(:traced) do
	      dummy_args = [nil]
	      dummy_args *= self.arity unless self.arity < 0

	      set_trace_func lambda { |event, file, line, id, bdng, cls|
	        if event == 'call'
	          set_trace_func nil
	          throw(:traced, eval('local_variables',bdng).map { |lv|  
lv.intern })
	        end
	      }

	      self.call(*dummy_args)

	      # if we get here, call is bust
	      set_trace_func nil
	      raise "No ruby method call in block"
	    end
	  end

	  def hcall(hash, &blk)
	    names = arg_names.reject { |n| n =~ /^(.*proc|bl(oc)?k)$/ }
	    call(*names.map { |n| hash[n] or raise "Missing argument" }, &blk)
	  end
	end

	def foo(a,b,c)
	  p [a,b,c]
	end

	method(:foo).hcall(:c => 'C', :a => 'A', :b => 'B')
	# => ["A", "B", "C"]

but it's block argument handling is very weak and it can't handle methods  
implemented in C. Better to just wait for Ruby 2.0. Personally, I've never  
once missed them anyway.

-- 
Ross Bamford - rosco@roscopeco.remove.co.uk