From: Stefano Crocco <stefano.crocco@...>
Date: 2009-06-13T18:54:10+09:00
Subject: Re: Noob question, regarding array

On Saturday 13 June 2009, Thiago wrote:
> |I'm a noob, trying to learn ruby.
> |I'm following along with the book  Programming Ruby, The Pragmatic
> |Programmer's Guide, which comes with ruby documentation.
> |
> |Im on chapter, Implementing a SongList Container, doing the code
> |samples, but i'm getting the following error when trying to run the
> |code:
> |18:in `append': undefined method `push' for nil:NilClass
> |(NoMethodError)
> |	from F:/InstantRails/rails_apps/test/test2.rb:80
> |
> |I have a SongList class with the following method:
> |
> |	def append(aSong)
> |		@songs.push(aSong)
> |		self
> |	end
> |
> |and im trying to run the code sample as in the book:
> |
> |list = SongList.new
> |list.
> |  append(Song.new('title1', 'artist1', 1)).
> |  append(Song.new('title2', 'artist2', 2)).
> |  append(Song.new('title3', 'artist3', 3)).
> |  append(Song.new('title4', 'artist4', 4))
> |
> |This doesnt make any sense. I can create the Song object just fine,
> |but if i try to add it to the array i get this erro.
> |Can anyone help me please?

What do you have in the initialize method of the SongList class? From the 
error message you get, it seems that @songs is nil instead of being an array. 
To avoid this, you need to set the @songs instance variable to an array and 
usually this is done in the initialize method. It should be something like 
this:

class SongList

  def initialize
    #other initialization code can go here 
    @songs = []
    #other initialization code can go here 
  end

end

I hope this helps

Stefano