From: luke gruber <luke.gru@...>
Date: 2011-11-13T12:14:44+09:00
Subject: Re: Advanced Ruby: Eval over multiple Bindings?

There doesn't seem to be a way to 'merge' the bindings, but there
are ways around it, I bet. This is kinda hacky but it works for
this simple case at least:

class Binding

  def +(other)
    raise "Other has to be a binding" unless Binding === other
    values = []
    instance_variables.each do |iv|
      values << "#{iv[1..-1]} = #{instance_variable_get(iv)}; "
    end
    other.instance_variables.each do |iv|
      values << "#{iv[1..-1]} = #{other.instance_variable_get(iv)}; "
    end
    binding.tap do |bind|
      bind.eval values.join
    end
  end

end

class Test
  def binding1
    a = 1
    binding.tap do |_b|
      local_variables.each do |lv|
        _b.instance_variable_set("@#{lv}", _b.eval(lv.to_s)) unless lv 
=~ /_b/
      end
    end
  end

  def binding2
    b = 2
    binding.tap do |bind|
      local_variables.each do |lv|
        _b.instance_variable_set("@#{lv}", _b.eval(lv.to_s)) unless lv 
=~ /_b/
      end
    end
  end

end

t = Test.new

puts eval('a + b', t.binding1 + t.binding2) # => 3

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