On Jul 27, 2009, at 3:21 PM, Ashley wrote:
> Hi Guys!
>
> Thanks for both of your input.
>
> I've opted for a helper method that looks something like:
>
> module UsersHelper
>
> def has_relationship_with?( other_user )
> var_name = "@has_relationship_with_#{other_user.id}"
> instance_variable_get(var_name) || instance_variable_set(var_name,
> current_user.has_relationship_with?( other_user )
> end
>
> end
>
> Loading all of the relationships was a little unnecessary in this case
> but making the same db query more than once per request was too so
> I've stuck the value in an instance variable
>
> you reckon that's ok?
Uh, a helper on the view? In this case, I'd say no.
I'm assuming that you really want to have several:
<%= "Interesting stuff" if @user.has_relationship_with?(@other_user) %>
<%= "Other stuff" if @user.has_relationship_with?(@other_user) %>
<%= "Boring stuff" if @user.has_relationship_with?(@other_user) %>
pieces in your view and you don't want 3 calls, only 1. Is that right?
If so, then your original solution may have done it. (ActiveRecord is
pretty smart most times.)
class User < ActiveRecord::Base
def has_relationship_with?( other_user )
relationships.find_by_other_user_id( other_user.id )
end
end
Once the relationships association is loaded, it might just get later
results from what's already in memory. Take a look at your log/
development.log and see if you find entries like: (but for
Relationship, of course)
School Load (0.000439) SELECT * FROM "schools" WHERE
("schools"."id" = 40882)
CACHE (0.000000) SELECT * FROM "schools" WHERE ("schools"."id" =
40882)
CACHE (0.000000) SELECT * FROM "schools" WHERE ("schools"."id" =
40882)
These are from a view helper (which in my case is actually an
ActiveRecord model backed by a real *database view* rather than a
table) that needs to find a record for the School model.
One thing to note is that you never have to say: !object.nil?
Just say: object
Since ruby only considers false and nil to be "false" in a boolean
context, it is idiomatic for predicates (i.e., methods that provide a
yes/no answer) to return false/true or nil/object. Since
find_by_other_user_id is already going to give you the Relationship
object when it exists and nil otherwise, you don't need to turn that
into false/true.
-Rob
> On Jul 27, 7:38 pm, James Englert <[email protected]> wrote:
>> You might want to memoize the results of that function to prevent
>> unnecessary hits to the database during the same request.
>>
>> On Mon, Jul 27, 2009 at 2:21 PM, Rob Biedenharn
>> <[email protected]>wrote:
>>
>>> On Jul 27, 2009, at 12:26 PM, Ashley wrote:
>>>> Hello guys!
>>
>>>> Question:
>>
>>>> Views should be "dumb" and models should deal with db queries...
>>
>>>> but what if you have a situation like so
>>
>>>> class User < ActiveRecord::Base
>>
>>>> def has_relationship_with?( other_user )
>>>> !relationships.find_by_other_user_id( other_user.id ).nil?
>>>> end
>>>> end
>>
>>>> and then in your view:
>>
>>>> <%= "Display this message" if @user.has_relationship_with?
>>>> (@other_user) %>
>>
>>>> Is it cool to call model methods which, in turn, query the db
>>>> within
>>>> the view or is there a better way of implementing this?
>>
>>>> Thanks
>>
>>>> ASH
>>
>>> This should be fine, but you might want to think about whether you
>>> need to "eager load" the relationships assosciation for performance.
>>
>>> The benefit is that your model contains the code and you can
>>> potentially refactor without touching your view.
>>
>>> -Rob
>>
>>> Rob Biedenharn http://agileconsultingllc.com
>>> [email protected]
>>
>> --
>> =====================
>> Jimhttp://www.thepeoplesfeed.com/contribute
> >
Rob Biedenharn http://agileconsultingllc.com
[email protected]
+1 513-295-4739
Skype: rob.biedenharn
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