From: daz <dooby@...10.karoo.co.uk>
Date: 2004-08-26T14:30:42+09:00
Subject: Re: Inheritance from built-in class


Nicolaj Soendberg-Madsen wrote:
> I have a question regarding inheritance from built-in classes. To simplify
> it, say I want to create a time-stamped array, which is an array with a
> time-stamp. Then I want to override the to_s method. I tried the following
> code:
>
>
> class Time_stamped_array < Array
>   def initialize
>     @time_stamp = Time.now
>   end
>
>   def to_s
>     super + " #{@time_stamp}"
>   end
>
> end
>
> ta = Time_stamped_array.new
>
> puts ta.to_s
>
>
> However this last call seems to invoke to_s in the super class (Array)
> and not in my new class. How do I do what I intented to do instead?
> Isn't it possible to override built-in methods?
>

That should be working, but your Time_stamped_array is empty
so only the date appears, I guess (?)


class Time_stamped_array < Array
  def to_s
    super + " #{Time.now}"
  end
end

ta = Time_stamped_array.new
ta.push('ab')  # add to Time_stamped_array
ta.push('cd')  #     - another -
p ta           #-> ["ab", "cd"]

puts ta.to_s   #-> abcd Thu Aug 26 09:10:11 ...


:daz