From: 1337p337 <1337p337@...>
Date: 2006-09-13T12:38:20+09:00
Subject: Re: Newbie Alert

This is actually easy to fix.  '+' is an undefined method for
nil:Nilclass, which means that the super on line 22 is returning nil.
'super' refers to the to_s of the parent class which is, Song#to_s:

> 01      class Song
...
> 07        def to_s
> 08          puts "Song: #{@name}--#{@artist} (#{@duration})"
> 09        end
> 10      end

The problem is the 'puts'.  puts prints a string and a "\n" to
standard out and returns nil.  You actually don't usually want to_s to
print anything, so if you change Song#to_s to read
	def to_s
		"Song: #{@name}--#{@artist} (#{@duration})"
	end
That will fix the bug, but your program won't print anything, because
aSong.to_s will just return a string (which is what you want).  So
you'll need to change lines 13 and 14:

> 13      print "aSong.to_s ==> "
> 14      aSong.to_s

to
	print "aSong.to_s ==> " + aSong.to_s + "\n"
or
	puts "aSong.to_s ==> #{aSong.to_s}"
and do something similar with lines 26 and 27.