# Dynamically set named\_scope based on current\_user

**URL:** <https://www.ruby-forum.com/t/dynamically-set-named-scope-based-on-current-user/182356>\
**Category:** Rails\
**Created:** [January 27, 2010, 12:03am UTC](https://www.ruby-forum.com/t/dynamically-set-named-scope-based-on-current-user/182356 "2010-01-27T00:03:47Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![jmaenpaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9de053/32.png) [@jmaenpaa](https://www.ruby-forum.com/u/jmaenpaa)\
**Post date:** [January 27, 2010, 12:03am UTC](https://www.ruby-forum.com/t/dynamically-set-named-scope-based-on-current-user/182356/1 "2010-01-27T00:03:47Z")

</div>

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.

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---

<div class="post-metadata">

**Author:** ![jmaenpaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9de053/32.png) [@jmaenpaa](https://www.ruby-forum.com/u/jmaenpaa)\
**Post date:** [January 27, 2010, 1:57pm UTC](https://www.ruby-forum.com/t/dynamically-set-named-scope-based-on-current-user/182356/2 "2010-01-27T13:57:16Z")

</div>

Given those relationships, you should be able to use  
current\_user.contact.site\_id.

---

<div class="post-metadata">

**Author:** ![jmaenpaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9de053/32.png) [@jmaenpaa](https://www.ruby-forum.com/u/jmaenpaa)\
**Post date:** [January 27, 2010, 2:25pm UTC](https://www.ruby-forum.com/t/dynamically-set-named-scope-based-on-current-user/182356/3 "2010-01-27T14:25:57Z")

</div>

site has many contacts through a polymorphic relationship:

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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