# Association extensions - has\_one

**URL:** <https://www.ruby-forum.com/t/association-extensions-has-one/87342>\
**Category:** Rails\
**Created:** [March 1, 2007, 10:30pm UTC](https://www.ruby-forum.com/t/association-extensions-has-one/87342 "2007-03-01T22:30:46Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![qwan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/q/9f8e36/32.png) [@qwan](https://www.ruby-forum.com/u/qwan)\
**Post date:** [March 1, 2007, 10:30pm UTC](https://www.ruby-forum.com/t/association-extensions-has-one/87342/1 "2007-03-01T22:30:46Z")

</div>

Hi,

I’m struggling with something that must be very common pattern, and  
want to do it the correct rails/ruby way but am a bit dense !

I have users - an admin user, registered users and a guest user (using  
ModelSecurity)

For many of linked associations I want the admin to be able to list or  
edit all instances, the registered user only their own one and guest  
none at all.

So somehow I want to over ride or extend the associations, or find, so  
that the condition is captured in one place and my controller/view  
code isn’t littered with these same if, else blocks…e.g something  
like…

```
   if(User.current.admin?)
      Theme.find(:all)
    elsif(User.current.registered?)
      User.current.theme
    else
      nil
    end

```

I’ve tried using the Association extensions so I can simply call  
something like

@theme = User.current.theme.find\_theme

e.g

class User \< ActiveRecord::Base

has\_one :theme do  
def find\_theme()  
if(admin?)  
Theme.find(:all)  
elsif(registered?)  
User.current.theme  
else  
[]  
end  
end  
end

But no joy, this gives method missing. If I change the association to  
has\_many however, it does work - but this is obviously not then  
correct with the model.

Do extensions only work for has\_many ?

Any advice on best place or pattern to encapsulate this kind of  
situation much appreciated.

Many thanks  
tom