Hello, I''ve got a problem with the inheritance as soon as I try to use it in a model. I''ve got plenty of items which can share a lot of code, so I created a class "Item", which inherits from ActiveRecord::Base, but because it''s not a "real item" but an interface, I set it abstract (writing abstract_class? method). Then I have all the differents items I can use (for instance: book,picture,...) which have their own class. I tried to write it down like : class Item < ActiveRecord::base def abstract_class? true end #stuff end class Book < Item def abstract_class? false end #stuff end The problem is, when I call Book.new.title I get an error saying that the method doesn''t exist (even if Book table has got a title column), and if I try Book.find(:first).title, it works.. I''ve got the impression that Book.new returns an Item instead of a Book ... Does anyone know how to fix my problem? Thanks a lot -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
You''ve defined abstract_class? as an instance method rather than as a class method. It''s a little less verbose to just do class Item < ActiveRecord::Base self.abstract_class = true end Fred --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Hi, I tryed that but the problem is still the same.. -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
What''s the actual code you''ve got, the actual error message you get and the database structure of the books table ? Fred --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
The code :
class Book < Item
has_and_belongs_to_many :collections
validates_presence_of :label
validates_presence_of :description
validates_uniqueness_of :label, :case_sensitive => false
include Element
UPLOAD_DIR="uploads/"
self.abstract_class=false
#methods
end
class Item < ActiveRecord::Base
attr_reader :product, :quantity
self.abstract_class=true
def initialize
@quantity = 1
end
def increment_quantity
@quantity += 1
end
def real_price
price * @quantity
end
end
The error:
You have a nil object when you didn''t expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.include?
Extracted source (around line #5):
2: <%=debug @element%>
3: <% fieldset_tag ''Book data'' do %>
4:
5: <%=@form.text_field :label%><br/>
6: <%=@form.text_area :description%><br/>
7: <%=@form.file_field :upload_file%>
8: <%end%>
The error :
#{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/base.rb:1844:in
`method_missing''
...
SQL query creating the Book table
CREATE TABLE `books` (
`id` int(11) NOT NULL auto_increment,
`label` varchar(255) default NULL,
`description` text,
`required_credits` int(11) default NULL,
`url` varchar(255) default NULL,
`price` int(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=33 DEFAULT CHARSET=latin1
If you need any other detail please let me know
thanks a lot
--
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In your initialize you need to call the super class initialize method (AR::Base''s initialize sets up some important stuff). Also I seem to recall that there are some issues involved with overriding AR::Base''s implementation of initialize. At the very least you need to make your initialize pass through any arguments or block specified to super Fred --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
At the moment I don''t have any initialize method ... I used the default constructor.. I tried to specify it calling super inside but still got the same error :/ -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Sure you do: def initialize @quantity = 1 end That should probably be def initialize(*args, &block) super(*args, &block) @quantity = 1 end Or, don''t define initialize at all and use an after_initialize callback. Fred --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Thanks a lot! That solved the problem. -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---