Saving class with array property with YAML

Ruby
1

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!

Best regards,
Martin.

2

Hi Martin, you have a few issues in your code, I will go through them
for you.

On 2/3/07, Martin Müller [email protected] wrote:

attr_accessor :title

def inititialize(author, title)

this should be spelled initialize, might be why you are getting an
argument error

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

you also need to:
require ‘yaml’

File.open(“testbook.yaml”, “w”) {|f| YAML.dump(testbook, f)}

Now it saves teh articles array

3

Thank you both for your kind help!

BR/Martin.

4

On 03.02.2007 17:13, Martin Müller wrote:

attr_accessor :title
attr_accessor :volume
end

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