From: Rob Biedenharn <Rob@...>
Date: 2008-02-07T13:04:06+09:00
Subject: Re: idiom I've not seen before

On Feb 6, 2008, at 10:55 PM, Rob Saul wrote:
> I came across this :
> 	elements.sort_by(&:position).each
> in something I've taken over.  I thought sort_by
> took a block.  Obviously I'm missing something.
> Can anyone shed some light on this trick?
>
> 	~Rob


You've found Symbol#to_proc

That line is equivalent to:

elements.sort_by {|e| e.send(:position) }.each

The "something" is a Rails project, isn't it?

== vendor/rails/activesupport/lib/active_support/core_ext/symbol.rb ==
class Symbol
   # Turns the symbol into a simple proc, which is especially useful  
for enumerations. Examples:
   #
   #   # The same as people.collect { |p| p.name }
   #   people.collect(&:name)
   #
   #   # The same as people.select { |p| p.manager? }.collect { |p|  
p.salary }
   #   people.select(&:manager?).collect(&:salary)
   def to_proc
     Proc.new { |*args| args.shift.__send__(self, *args) }
   end
end


I don't know how you can send additional arguments however.

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com