Question

I am following the tinyclone example in Cloning Internet Application with Ruby and is trying to create an object to be stored into mysql.

However, whenever I try to create a Url object (see code below), the result is always
“=> Url @id=nil @original=”http://www.gmail.com” @link_identifier=nil”

The id is not created nor the data is stored in the database. The link to the sql database is correct as I already tried dropping the database and recreating it using DataMapper.auto_migrate!

Can anyone help? Thanks.

DataMapper.setup(:default,'mysql://root@localhost/tinyclone')

class Url
  include DataMapper::Resource
  property  :id,          Serial
  property  :original,    String, :length => 255   
  belongs_to  :link
end

class Link
  include DataMapper::Resource
  property  :identifier,  String, :key => true
  property  :created_at,  DateTime 
  has 1, :url
  has n, :visits
end

DataMapper.finalize

url = Url.create(:original => 'http://www.gmail.com')
=> #<Url @id=nil @original="http://www.gmail.com" @link_identifier=nil>

Answer 1

In your Url model Link is a required association. You can’t create a url without a link because validation will fail. If you want to be able to create urls without associating them with a link you can write belongs_to :link, :required => false