# Controller Problem **URL:** \ **Category:** Rails\ **Created:** [November 7, 2008, 6:11pm UTC](https://www.ruby-forum.com/t/controller-problem/152816 "2008-11-07T18:11:37Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![kerouak](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6de8d8/32.png) [@kerouak](https://www.ruby-forum.com/u/kerouak)\ **Post date:** [November 7, 2008, 6:11pm UTC](https://www.ruby-forum.com/t/controller-problem/152816/1 "2008-11-07T18:11:37Z")
I have this action in questions\_controller.rb : def arg @questions = Question.find(:all) respond\_to do |format| format.html format.xml { render :xml =\> @questions } end end Why this action doesn’t work ? It is the same as index action, but this one doesn’t work. The error is: “Couldn’t find Question with ID=arg” ---
**Author:** ![kerouak](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6de8d8/32.png) [@kerouak](https://www.ruby-forum.com/u/kerouak)\ **Post date:** [November 7, 2008, 7:16pm UTC](https://www.ruby-forum.com/t/controller-problem/152816/2 "2008-11-07T19:16:00Z")
> The error is: “Couldn’t find Question with ID=arg” What’s the url that is supposed to be invoking the arg action? What do your routes look like? rake routes \>routes.lst then browse that file to see the routes that are available it seems that ‘arg’ is being interpreted as an id parameter for an existing route… if you want arg as an action for the whole collection, then I’d expect to see something like map.resources :questions, :collection =\> {:arg =\> :get} in routes.rb to add that as a recognized route If it’s for a specific question, then map.resources :questions, :member =\> {:arg =\> :get} ---
**Author:** ![kerouak](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6de8d8/32.png) [@kerouak](https://www.ruby-forum.com/u/kerouak)\ **Post date:** [November 7, 2008, 7:43pm UTC](https://www.ruby-forum.com/t/controller-problem/152816/3 "2008-11-07T19:43:29Z")
> What’s the url that is supposed to be invoking the arg action? [http://localhost:3000/questions/arg](http://localhost:3000/questions/arg) > if you want arg as an action for the whole collection, then I’d expect > to see something like > > map.resources :questions, :collection =\> {:arg =\> :get} That way it works. But can you explain me the reason ? What’s the meaning of the parameter :collection =\> {:arg =\> :get} ? Every time i create a new action, I have to update the routes.rb file ?? ---
**Author:** ![kerouak](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6de8d8/32.png) [@kerouak](https://www.ruby-forum.com/u/kerouak)\ **Post date:** [November 7, 2008, 7:59pm UTC](https://www.ruby-forum.com/t/controller-problem/152816/4 "2008-11-07T19:59:15Z")
Davide S. wrote: > > What’s the url that is supposed to be invoking the arg action? > > [http://localhost:3000/questions/arg](http://localhost:3000/questions/arg) > > > if you want arg as an action for the whole collection, then I’d expect > > to see something like > > > > map.resources :questions, :collection =\> {:arg =\> :get} > > That way it works. But can you explain me the reason ? > What’s the meaning of the parameter :collection =\> {:arg =\> :get} ? > > Every time i create a new action, I have to update the routes.rb file ?? That is true, yes. The RESTful design methodology requires you to define custom actions in your routes file. That is because earlier when we used map.connect ‘:controller/:action/:id’ we always used the GET method - for the destroy, create and update actions. Then someone found out that you could make the urls prettier (and respect the RESTful design philosophy) by using other standard HTTP methods like DELETE, POST and PUT. Therefore you have to actually tell Rails what method you’ld like to use, it will not use GET by default. That is actually good. Imagine having half of your custom actions being using the GET method, the other half using the POST, PUT or DELETE method. Then you’ld need to define what method to use for half of them in your routes file (instead of all of them). What a mess… (: ---
**Author:** ![kerouak](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6de8d8/32.png) [@kerouak](https://www.ruby-forum.com/u/kerouak)\ **Post date:** [November 7, 2008, 8:11pm UTC](https://www.ruby-forum.com/t/controller-problem/152816/5 "2008-11-07T20:11:20Z")
> That is true, yes. The RESTful design methodology requires you to define > custom actions in your routes file. That is because earlier when we used > map.connect ‘:controller/:action/:id’ we always used the GET method - > for the destroy, create and update actions. > > Then someone found out that you could make the urls prettier (and > respect the RESTful design philosophy) by using other standard HTTP > methods like DELETE, POST and PUT. Therefore you have to actually tell > Rails what method you’ld like to use, it will not use GET by default. > That is actually good. Imagine having half of your custom actions being > using the GET method, the other half using the POST, PUT or DELETE > method. Then you’ld need to define what method to use for half of them > in your routes file (instead of all of them). What a mess… (: So, if i don’t specify a method (as we did), the default one would be POST ?? Or DELETE ?? Or PUT ?? Which one ?? ---
**Author:** ![kerouak](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6de8d8/32.png) [@kerouak](https://www.ruby-forum.com/u/kerouak)\ **Post date:** [November 7, 2008, 8:52pm UTC](https://www.ruby-forum.com/t/controller-problem/152816/6 "2008-11-07T20:52:49Z")
Davide S. wrote: > > That is true, yes. > So, if i don’t specify a method (as we did), the default one would be > POST ?? > Or DELETE ?? > Or PUT ?? > > Which one ?? Sorry for being a little unclear but this was my point: Rails will NOT try to guess which method you want and there is no default. In other words, since we don’t only use GET now, we have to tell Rails which one to use (no matter if it’s GET, POST, PUT or DELETE). map.resources :questions, :collection =\> {:arg =\> :get} In the example above we pass an option called :collection that specifies which custom actions that is going to affect a _collection_ of (in your case) questions. Then we define one custom action (“arg”) that is going to use the GET method. See the point? :arg =\> :get The collection option accepts a hash with action name as key and method name (GET, POST, PUT, DELETE) as value, so there is no default. Also remember that if you want to make an action that is only going to affect _one_ question you’ll want to use the :member option instead, like this: map.resources :questions, :collection =\> {:arg =\> :get}, :member =\> {:affecting\_one\_question =\> :get} Hope that helped. (: ---
**Author:** ![kerouak](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/6de8d8/32.png) [@kerouak](https://www.ruby-forum.com/u/kerouak)\ **Post date:** [November 7, 2008, 9:49pm UTC](https://www.ruby-forum.com/t/controller-problem/152816/7 "2008-11-07T21:49:34Z")
> That way it works. But can you explain me the reason ? > What’s the meaning of the parameter :collection =\> {:arg =\> :get} ? > > Every time i create a new action, I have to update the routes.rb file ?? [http://api.rubyonrails.org/classes/ActionController/Resources.html](http://api.rubyonrails.org/classes/ActionController/Resources.html)