From: Deepak Gole <deepak.gole8@...>
Date: 2008-02-08T20:33:35+09:00
Subject: Re: idiom I've not seen before

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  Hello Rob

  We can send arguments, Following is the way, But it throws an error.

  def to_proc
    Proc.new { |*args| args.shift.__send__(self, *args) }
  end

  arr.collect(&[:concat,"Rocking"])

 *   *sample.rb:41:in `__send__': [:concat, "dee"] is not a symbol
(TypeError)
    from sample.rb:41:in `to_proc'
    from sample.rb:51:in `collect'
    from sample.rb:51

 But if we change the implementation of to_proc then it works.

   def to_proc
      lambda {|target| target.send *self}
   end

   arr.collect(&[:concat,"Rocking"])

 o/p => ["rubyRocking", "railsRocking", "rjaxRocking"]

 I don't  know how.


On Feb 6, 2008 8:04 PM, Rob Biedenharn <Rob@agileconsultingllc.com> wrote:

> 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
>
>
>
>

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