From: Markus n/a <lists@...>
Date: 2013-01-03T00:40:28+09:00
Subject: Re: temporarily override a methode

found a way

class Tee
  def self.tee(logfile, append = true, stdout = true, stderr = true)
    file = File.open(logfile, append ? 'a' : 'w+')
    stdout_write = nil
    stderr_write = nil
    stdout_write = decorate($stdout, :write) {|data| file.write(data)} 
if stdout
    stderr_write = decorate($stderr, :write) {|data| file.write(data)} 
if stderr
    begin
      yield if block_given?
    ensure
      restore($stdout, :write, stdout_write) if not stdout_write.nil?
      restore($stderr, :write, stderr_write) if not stderr_write.nil?
      file.close
    end
  end

  private
  def self.restore(obj, methodname, method)
    class << obj
      self
    end.module_eval do
      define_method(methodname, method)
    end
  end
  def self.decorate(obj, methodname)
    method = obj.method(methodname)
    class << obj
      self
    end.module_eval do
      define_method(methodname) do |data|
        method.call(data)
        yield data
      end
    end
    return method
  end
end

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