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
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 > > ASHThis 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 Rob-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org
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 <Rob-GBZH0y1GwQfnZcttdmLDtcI/UQi/AW5J@public.gmane.org>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 > Rob-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org > > > > > >-- ====================Jim http://www.thepeoplesfeed.com/contribute --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
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?
On Jul 27, 7:38 pm, James Englert
<englert.ja...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
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
> <R...-GBZH0y1GwQfnZcttdmLDtcI/UQi/AW5J@public.gmane.org>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
> > R...-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org
>
> --
> ====================> Jimhttp://www.thepeoplesfeed.com/contribute
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 <englert.ja...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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 >> <R...-GBZH0y1GwQfnZcttdmLDtcI/UQi/AW5J@public.gmane.org>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 >>> R...-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org >> >> -- >> ====================>> Jimhttp://www.thepeoplesfeed.com/contribute > >Rob Biedenharn http://agileconsultingllc.com Rob-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org +1 513-295-4739 Skype: rob.biedenharn