From: John Merlino <stoicism1@...>
Date: 2010-01-27T08:52:55+09:00
Subject: Re: dynamically set named_scope based on current_user

John Merlino wrote:
> 
> 
> Hey all,
> I keep getting the following 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.size
> 
> Based on the current user, when they navigate to a page, I want to limit
> them to what they can see based on their site. Problem is there is no
> association between site and user table directly. A contact has_one user
> (user information is stored in current_user variable). A site has_many
> contacts. And a site has_many students, where students table has a
> foreign key of site_id. So there is a link between students and site, so
> when the current user navigates to students page, they can only see
> students from same site as them. I can do this by hard coding a number
> in a named_scope to only display students for the site of the
> current_user. But different users will belong to different sites so when
> logged in, the site their associated with will change. That's the
> problem - to dynamically set that value in a named_scope. This is what I
> have:
> 
> StudentsController
> 
> def index_scoper
>   if current_user.role_id == 8
>     super.site_staff_limit while current_user[:site_id] #The problem is
> the user table has no site_id. There is no direct link between the users
> table and sites table. However, there is a link between users and
> contacts and then site and contacts and then site and students, where
> students table has site_id.
>   else
>     super.with_state.with_site
>   end
> end
> 
> Student Model
>     named_scope :site_staff_limit, lambda {|site_id| {:conditions =>
> {:site_id => site_id}}}
> 
> Thanks for any suggestions.

relationship between tables:

users: contact_id
contact: primary key, contactable_id, contactable_type
site: primary key
student: site_id

User model
belongs_to :contact

Contact model
has_one :user
belongs_to :contactable,  :polymorphic => true, :dependent => :destroy

Site model
 has_many :contacts, :as => :contactable
has_many :students

Students model
belongs_to :site

This successfully limits the students by site:
StudentsController
def index_scoper
  if current_user.role_id == 8
    super.site_staff_limit
  else
    super.with_state.with_site
  end
end

Students model
named_scope :site_staff_limit, :conditions => {:site_id => 1}

The problem is different users will belong to different sites, so they 
can only access student records of the site they belong to. I am having 
difficulty making that named_scope above dynamic enough to accomplish 
this.
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