Rails - Oct 2005 - Searching an attribute in a hmabtm relationship

(Nuby to Ruby and Rails...)
I''ve implemented security using the login generator in a simple app so
that I have a user table, a roles table, and a join between them
(roles_users). All works as expected. I now need to check if a user
has a specific role, but my approach is off somehow.

Here''s what I''ve tried thusfar:

          user_roles = @session[:user].roles
          user_roles.find { |r| r.name == "officer"}

When this executes, I get "can''t locate Role without ID...".
What I
*thought* I was doing was searching an array (user_roles) for a value,
but this seems to imply that I''ve doing a db search. What am I missing
here? Is there a better way to approach this? (I''ve checked, and
user_roles does hold the correct list of objects...)

TIA,
Keith

On 12-okt-2005, at 0:12, Keith Lancaster wrote:
> (Nuby to Ruby and Rails...)
> I''ve implemented security using the login generator in a simple
app so
> that I have a user table, a roles table, and a join between them
> (roles_users). All works as expected. I now need to check if a user
> has a specific role, but my approach is off somehow.
>
> Here''s what I''ve tried thusfar:
>
>           user_roles = @session[:user].roles
>           user_roles.find { |r| r.name == "officer"}
>
> When this executes, I get "can''t locate Role without
ID...". What I
> *thought* I was doing was searching an array (user_roles) for a value,
> but this seems to imply that I''ve doing a db search. What am I
missing
> here? Is there a better way to approach this? (I''ve checked, and
> user_roles does hold the correct list of objects...)
find in this case is overridden and hooked into AR''s find.

What you need I assume is this:

allow_access if @session[:user].roles.include?(Role.find_by_name 
("officer"))

-- 
Julian "Julik" Tarkhanov

On Oct 11, 2005, at 9:10 PM, Julian ''Julik'' Tarkhanov wrote:
>
> On 12-okt-2005, at 0:12, Keith Lancaster wrote:
>
>
>> (Nuby to Ruby and Rails...)
>> I''ve implemented security using the login generator in a
simple
>> app so
>> that I have a user table, a roles table, and a join between them
>> (roles_users). All works as expected. I now need to check if a user
>> has a specific role, but my approach is off somehow.
>>
>> Here''s what I''ve tried thusfar:
>>
>>           user_roles = @session[:user].roles
>>           user_roles.find { |r| r.name == "officer"}
>>
>> When this executes, I get "can''t locate Role without
ID...". What I
>> *thought* I was doing was searching an array (user_roles) for a  
>> value,
>> but this seems to imply that I''ve doing a db search. What am I
>> missing
>> here? Is there a better way to approach this? (I''ve checked,
and
>> user_roles does hold the correct list of objects...)
>>
>
> find in this case is overridden and hooked into AR''s find.
>
> What you need I assume is this:
>
> allow_access if @session[:user].roles.include?(Role.find_by_name 
> ("officer"))
>
> -- 
> Julian "Julik" Tarkhanov
>
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>

Or you can  do it like this to make sure it uses the array version of  
find and not the AR one:
>> user_roles.to_a.find { |r| r.name == "officer"}
HTH-
-Ezra Zygmuntowicz
WebMaster
Yakima Herald-Republic Newspaper
ezra-gdxLOakOTQ9oetBuM9ipNAC/G2K4zDHf@public.gmane.org
509-577-7732

Ezra Zygmuntowicz <ezra@...> writes:
> 
> 
> On Oct 11, 2005, at 9:10 PM, Julian ''Julik'' Tarkhanov
wrote:
> >
> > find in this case is overridden and hooked into AR''s find.
> >
> > What you need I assume is this:
> >
> > allow_access if  <at>
session[:user].roles.include?(Role.find_by_name
> > ("officer"))
> >
I''m certain you are right, but I''m not certain why :-). Being
new to ruby,
perhaps I''m not understanding an aspect of containers or inheritance in
ruby.
Are you saying that the find method in the role object, which is contained in
the array, is overriding the find method in the array? IOW, does a method in the
contained class override a method in the container? 

Keith

On Oct 12, 2005, at 6:34 AM, Keith wrote:
> Ezra Zygmuntowicz <ezra@...> writes:
>
>
>>
>>
>> On Oct 11, 2005, at 9:10 PM, Julian ''Julik'' Tarkhanov
wrote:
>>
>
>
>>>
>>> find in this case is overridden and hooked into AR''s find.
>>>
>>> What you need I assume is this:
>>>
>>> allow_access if  <at> session[:user].roles.include? 
>>> (Role.find_by_name
>>> ("officer"))
>>>
>>>
>
> I''m certain you are right, but I''m not certain why :-).
Being new
> to ruby,
> perhaps I''m not understanding an aspect of containers or  
> inheritance in ruby.
> Are you saying that the find method in the role object, which is  
> contained in
> the array, is overriding the find method in the array? IOW, does a  
> method in the
> contained class override a method in the container?
>
> Keith
>
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
     Well ActiveRecord collections have their own find method that  
finds stuff from the database. So the :conditions string gets turned  
into the where clause in an SQL statement. Like this:
>> user_roles.find :all, :conditions => "role = officer"
But the standard Array class has a find method that takes a block and  
returns the elements of the array that return true when evaluated in  
the block. So if you cast your AR collection with a .to_a (to array)  
method you don;t loose any info but when you call the .find method  
after the cast it uses the find method that it looks up in the Array  
class. Whereas Active Record defines its own find method that works  
with the database.
     You use the to_a method to make sure that the Array#find method  
is used and not the ActiveRecord#find method. Note that the  
user_roles collection must be pre populated from the db already:
>> user_roles.to_a.find { |r| r.name == "officer"}

     Active record collections behave like Array collections except  
they are populated from the db and the find method is different from  
a standard array.


HTH-
-Ezra Zygmuntowicz
Yakima Herald-Republic
WebMaster
http://yakimaherald.com
509-577-7732
ezra-gdxLOakOTQ9oetBuM9ipNAC/G2K4zDHf@public.gmane.org