如何创建一个在传递块时初始化和关闭的Ruby类？

Ruby有File类,可以使用普通的new()方法初始化,或者使用open()并传递一个块.我怎么写一个表现得像这样的课？

File.open("myfile.txt","r") do |f|
...
end

这是将块传递给new / open方法的简单示例

class Foo
  def initialize(args, &block)
    if block_given?
       p block.call(args) # or do_something
    else
      #do_something else
    end

  end

  def self.open(args, &block)
    if block_given?
      a = new(args, &block)  # or do_something
    else
      #do_something else
    end
  ensure
    a.close
  end

  def close
     puts "closing"
  end


end

Foo.new("foo") { |x|  "This is #{x} in new" } 
# >> "This is foo in new"
Foo.open("foo") { |x|  "This is #{x} in open" } 
# >> "This is foo in open"
# >> closing