From: John Maclean <info@...>
Date: 2006-01-21T06:37:54+09:00
Subject: Re: Basic Inheritance questions {noob alert:- pickaxe ed. 2, page 27}

Thanks for that speedy reply. I've decided to require the within the
child. One thing to note is that when I do require the child irb shows
the following..

cat fx/ruby/chap3/class_KaraokeSong.rb

#!/usr/bin/env ruby 
require 'class_Song.rb'

# test if this class has been loaded correctly
Object.const_defined?(:Song)

class KaraokeSong < Song
  def to_s
    super + " [#@lyrics]" 
  end 
end

irb(main):011:0> require 'class_KaraokeSong.rb'
=> false



On Sat, 21 Jan 2006 04:28:25 +0900 Wilson Bilkovich
<wilsonb@gmail.com> wrote:

> You can do it one of three ways:
> In IRB, require the Song file, and then the KaraokeSong file, in that
> order. Edit the KaraokeSong file to require the Song before defining
> the child class. Put both of the class definitions in a single file,
> with the parent first, and then the child.
> 
> In order for KaraokeSong < Song to work, this method needs to return
> true: Object.const_defined?(:Song)
> That will be the case with each of the three possibilities above.
> 
> Good luck, and have fun,
> --Wilson.
> 
> On 1/20/06, John Maclean <info@jayeola.org> wrote:
> > Chaps,
> >
> > Say you have a class Song. You'd make a file for that class with the
> > following;
> >
> > #!/usr/bin/env ruby
> > class Song
> >   def initialize(name, artist, duration)
> >     # define instance variables
> >     @name = name
> >     @artist = artist
> >     @duration = duration
> >   end
> >
> >   def to_s
> >     # method for displaying these instancess
> >   "Song: #@name--#@artist (#@duration)"
> >   end
> > end
> >
> > # test the class by creating a new object
> > #song = Song.new("Bicylops", "Fleck", 260)
> > #song.inspect
> >
> > Now it's time to make a "child" class....
> >
> > jayeola@tp20$ cat class_KaraokeSong.rb
> > #!/usr/bin/env ruby
> > class KaraokeSong < Song
> >   def initialize(name, artist, duration, lyrics)
> >     super(name, artist, duration)
> >     @lyrics = lyrics
> >   end
> >
> > #  def to_s
> > #    # method for displaying these instancess
> > #  "Song: #@name--#@artist (#@duration)"
> > #  end
> > end
> >
> > When I created the parent it was simple to `irb` and then `require
> > class_Song.rb`.
> >
> > How would one use this child class? Not quite clear from the Pickaxe
> > book. Do I create a new file for KaraokeSong as I have done or have
> > both the "super" and "child" in the same file?
> >
> >  --
> > John Maclean
> > MSc (DIC)
> > 07739 171 531
> >
> >
> >
> 
> 
> 


-- 
John Maclean
MSc (DIC)
07739 171 531