Binding趣用

昨天看到一段代码，感觉挺有趣，贴出来分享给大家。

class BindingDemo
  def initialize
    @ivar = "wombat in instance variable"
  end
  def get_binding(param)
    lvar = "cat in local variable"
    binding
  end
end

b = BindingDemo.new

the_binding = b.get_binding("dog in paramater") { "elk in block" }

puts(eval("@ivar", the_binding))
puts(eval("lvar", the_binding))
puts(eval("param", the_binding))
puts(eval("yield", the_binding))

eval("lvar = 'new value'", the_binding)
puts(eval("lvar", the_binding))

解释哈 趣味何在？？

执行下不就知道了。

eval("lvar = 'new value'", the_binding)  
puts(eval("lvar", the_binding))


这个输出 "new value"怎么解释？？我只能强行理解的

eval是在当前定上下文中去执行代码，由此可知，eval("lvar = 'new value'", the_binding) 是在the_binding上下文中给变量ivar重新赋值为'new value'.
那么puts(eval("lvar", the_binding)) 理所当然应该输出'new value'