I have two tables, user & provider and I''m struggling to set up the
association between them.
A simplified table structure for the two is:
CREATE TABLE users (
id integer not null,
login string not null,
password string not null
)
CREATE TABLE providers (
id integer not null,
user_id integer not null,
...
)
and I''ve used the generater to create two modules, as follows (cut
down)
class User < ActiveRecord::Base
has_one :provider
def invoices_raised
provider.get_invoices
end
....
end
class Provider < ActiveRecord::Base
has_many :invoices
belongs_to :user
def get_invoices
invoices.find(:all)
end
end
I have a controller that calls invoices_raised :
class AccountController < ApplicationController
model :user
before_filter :get_invoices
def get_invoices
@user = User.find(@session[''user''].id)
@invoices_raised = @user.invoices_raised
end
...
end
but inside the invoices_raised method I get the following error:
You have a nil object when you didn''t expect it!
The error occured while evaluating nil.get_invoices
I thought that using belongs_to & has_one was supposed to implicitly
create a provider instance for me?
--
-S
Sports Photography in South Yorkshire & Derbyshire
http://www.stuartgrimshaw.co.uk
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Stuart Grimshaw wrote:> I have two tables, user & provider and I''m struggling to set up the > association between them.{...}> class User < ActiveRecord::Base > has_one :provider > > def invoices_raised > provider.get_invoices > end > end > > but inside the invoices_raised method I get the following error: > > You have a nil object when you didn''t expect it! > The error occured while evaluating nil.get_invoices > > I thought that using belongs_to & has_one was supposed to implicitly > create a provider instance for me? > > -- > -SUser.has_one :provider will create an accessor on your User class that retrieves the Provider associated with a given user u (i.e. select * from providers where providers.user_id=u.id). There''s not enough info in your post to determine why this method is returning a nil for your User instance; I would need to see the object that you are calling get_invoices on and how it is created. I would recommend brushing up on what the associations methods do (belongs_to, has_many, etc), and you will likely discover the source of the error For example...> class Provider < ActiveRecord::Base > has_many :invoices > belongs_to :user > > def get_invoices > invoices.find(:all) > end > endCalling has_many :invoices actually creates an instance method "invoices" in Provider that returns all Invoice objects associated with your Provider instance. I''m guessing that this is what you hoped to achieve with get_invoices. I''m not sure what you''re expecting from your call "invoices.find(:all)". The invoices method returns all Invoice objects associated with your Provider instance, and "find" is actually an ActiveRecord::Base class method which will raise an error when you call it on a collection of Invoices, which is what you''re doing here. find(:all) retrieves _all_ records from a particular table, and I''m guessing that''s not what you''re trying to do here. If it is, you''ll want to call Invoice.find(:all) I would recommend checking out the Rails documentation for associations: http://api.rubyonrails.org/ (click on ActiveRecord::Associations::ClassMethods in the Class frame) Hope this helps - Bryan -- 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 -~----------~----~----~----~------~----~------~--~---
Stuart Grimshaw wrote:> > class User < ActiveRecord::Base > has_one :provider > > def invoices_raised > provider.get_invoices > end > > .... > > endWhat if you change "provider.get_invoices" to "self.provider.get_invoices"? -- 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 -~----------~----~----~----~------~----~------~--~---
Bryan Duxbury wrote:> Stuart Grimshaw wrote: > >> >> class User < ActiveRecord::Base >> has_one :provider >> >> def invoices_raised >> provider.get_invoices >> end >> >> .... >> >> end > > What if you change "provider.get_invoices" to > "self.provider.get_invoices"?If you omit the receiver, it defaults to self. i.e. "provider.get_invoices" is interpreted as being equal to "self.provider.get_invoices" Here is a good link if you want to learn more about this or see some examples: http://www.rubycentral.com/book/tut_methods.html -- 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 -~----------~----~----~----~------~----~------~--~---
Bryan Evans wrote:> User.has_one :provider will create an accessor on your User class that > retrieves the Provider associated with a given user u (i.e. select * > from providers where providers.user_id=u.id). There''s not enough info in > your post to determine why this method is returning a nil for your User > instance; I would need to see the object that you are calling > get_invoices on and how it is created.get_invoices is called : before_filter :get_invoices, :only => [:my_account] Thanks for the reply Bryan, I know my understanding of asscociations is poor, and I have read the docs again now (and tbh, I think I need to again) but at that time in the morning, it seemed like the best thing to do .. ;-) -S --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---