From: Robert Klemme <shortcutter@...>
Date: 2007-02-04T02:00:05+09:00
Subject: Re: Saving class with array property with YAML


On 03.02.2007 17:13, Martin M�ller wrote:
> Hello
> 
> I'm new to Ruby and unfortuantly I can't find an example anywhere to the 
> following problem.
> 
> I have the following class:
> 
> 
> class Article
>   attr_accessor :author
>   attr_accessor :title
> 
>   def inititialize(author, title)
>     @autor = author
>     @title = title
>   end
> end
> 
> 
> class Book
>   attr_accessor :year
>   attr_accessor :volume
>   attr_accessor :articles       # array of articles
> 
>   def initialize(year, volume)
>     @year     = year
>     @volume   = volume
>     @articles = Array.new
>   end
> 
>   def insert(author, title)
>     @articles.push(Article.new(author,title))
>   end
> end
> 
> 
> class Bookshelf
> ...
> end
> 
> 
> #create book
> testbook = Book.new(2007, 1)
> 
> #insert 2 articles into the book
> testbook.insert("Martin Mueller", "Confessing that I'm a Ruby Dummy")
> testbook.insert("Hillary Clinton", "Elect me and Ruby will save our 
> planet")
> 
> 
> #write Book to YAML
> File.open("testbook.yaml", "w") {|f| YAML.dump(testbook, f)}
> 
> -----------------------
> 
> My question is: how can I bring Ruby to save also the Array??
> 
> I played around with  to_yaml_properties but without success.
> 
> thanks a lot for any hint!

First you should correct spelling errors of your initialize methods. 
After you did that, you don't have to do anything:

irb(main):049:0> testbook = Book.new(2007, 1)
=> #<Book:0x4918fe4 @year=2007, @articles=[], @volume=1>
irb(main):050:0> testbook.insert("Martin Mueller", "Confessing that I'm 
a Ruby Dummy")
=> [#<Article:0x4914e94 @title="Confessing that I'm a Ruby Dummy", 
@autor="Martin Mueller">]
irb(main):051:0> testbook.insert("Hillary Clinton", "Elect me and Ruby 
will save our planet")
=> [#<Article:0x4914e94 @title="Confessing that I'm a Ruby Dummy", 
@autor="Martin Mueller">, #<Article:0x491090c @title=
"Elect me and Ruby will save our planet", @autor="Hillary Clinton">]
irb(main):052:0> puts testbook.to_yaml
--- !ruby/object:Book
articles:
- !ruby/object:Article
   autor: Martin Mueller
   title: Confessing that I'm a Ruby Dummy
- !ruby/object:Article
   autor: Hillary Clinton
   title: Elect me and Ruby will save our planet
volume: 1
year: 2007
=> nil
irb(main):053:0>

Btw, your Book#insert does two things: create an Article and append that 
to your Book.  It's a convenient method.  You don't really need that 
method since you make #articles available anyway so you could as well do:

testbook.articles << Article.new( "Martin", "I am a Ruby" )

Kind regards

	robert