From: Josh Cheek <josh.cheek@...>
Date: 2011-11-15T08:53:48+09:00
Subject: Re: Binding#with

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On Mon, Nov 14, 2011 at 10:41 AM, Intransition <transfire@gmail.com> wrote:

> Well, this seems to work:
>
>   #
>   def with(_hash, &_yield)
>     _hash = (_hash || {}).to_hash
>     code = <<-END
>       define_method(:_with) do |#{_hash.keys.join(',')}|
>         binding
>       end
>     END
>     (class << self; self; end).class_eval(code)
>     b = _with(*_hash.values, &_yield)
>     (class << self; self; end).class_eval{ remove_method(:_with) }
>     return b
>     #eval("Proc.new{ |#{_hash.keys.join(',')}| binding
> }").call(*_hash.values)
>   end
>
> But alas, now I am loosing the context of original binding. Why is that? I
> thought define_method kept closure.
>
>
Not sure what you mean, it seems to work for me:


class Binding
  def with(_hash={}, &_yield)
    singleton_class.class_eval(<<-CODE)
      define_method :_with do |#{_hash.keys.join(',')}|
        binding
      end
    CODE
    bnd = _with(*_hash.values, &_yield)
    singleton_class.class_eval { remove_method :_with }
    bnd
  end
end

RUBY_VERSION # => "1.9.3"
binding.with(:a => 10) { |x| x + x }.eval('yield a + 5')  # => 30

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