From: Sebastian Hungerecker <sepp2k@...>
Date: 2009-01-28T08:27:52+09:00
Subject: Re: String doesnt auto dup on modification

Simon Krahnke wrote:
> * Mike Gold <mike.gold.4433@gmail.com> (2009-01-23) schrieb:
> >     String.public_instance_methods(false).grep(/!/).map(&:to_sym) +
>
> Is that a new feature?

Symbol#to_proc is new in ruby core since 1.8.7+. It had been previously 
defined by ActiveSupport and, I think, facets.

> make the to_sym method act as block. Which to_sym method?

The to_sym method of each item in the array. symbol_to_proc is defined 
somewhat like:
lambda {|x, *args| x.send(self, *args)}
So foo.map(&:to_sym) behaves like foo.map {|x| x.send(:to_sym)}


> >   DESTRUCTIVE_METHODS.each { |m|
> >     define_method(m) { |*args, &block|
> >       __setobj__(__getobj__.dup)
> >       __getobj__.send(m, *args, &block)
>
> WTF? What's this __[gs]etobj__ about?

Those are methods defined by DelegateClass(). They are used to get and set the 
object that is delegated to. In this case they cause the proxy-object to 
delegate to a copy of the original string instead of the original string 
itself when a destructive method is called.

HTH,
Sebastian
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