Ruby - redefining instance methods not working

My simple attempt to redefine instance methods are not working

class File
  alias_method :old_atime, :atime
  def atime(*args)
    puts "helllllo"
    old_atime(*args)
  end
end


f = File.new("C:\\abc.txt","w")
puts f.atime

An开发者_如何学Pythony idea why?

I'm attempting to print "helllllo" everytime File#atime is called. Even alias old_atime atime is not working.

Is there something I'm doing wrong here?

Above code works perfectly as it should be. Puts "helllllo" writes "helllllo" in to your opened file. Puts inside the file instance meant for writing.

Just call f.close and open your file in text editor. You can see the content.

Yep, Ramesh is right. Try this:

class File
  alias_method :old_atime, :atime
  def atime(*args)
    Kernel.puts "helllllo"   # <---- Kernel method
    old_atime(*args)
  end
end


f = File.new("C:\\abc.txt","w")
puts f.atime

The issue is that 'puts' is defined in File for writing to files. You want the Kernel one which is used unless defined in a more specific scope.

This should work fine, but IO#puts writes to the IO object itself, not STDOUT. In other words, it's writing to the file.

Call f.atime a few times and then f.close within irb and you should see it printing helllllo to the file for each call to atime.

To print to STDOUT, you could use $stdout.puts or Kernel.puts.