Error using ActiveResource with Rails 3 and REST API - ruby-on-rails

Question

I have a REST API that I am trying to access using Rails 3.0.1 that returns:
<Sessions>
<Session>
<Title>This is a sample title</Title>
...Misc
</Session>
<Session>
<Title>Another Title</Title>
...Misc
</Session>
</Sessions>
I have set up my session.rb class defined:
class Session < ActiveResource::Base
self.site = "http://example.com/rest"
end
The url that will return the XML is http://example.com/rest/sessions.
I then have a controller that is defined as this:
class HomeController < ApplicationController
def index
Session.all
end
end
and my view, index.html.erb, is defined:
<h1>List Sessions</h1>
<% #sessions.each do |session| %>
<div><%= session.title %></div>
<% end %>
When I try to view this page, I get the following error:
NoMethodError in HomeController#index
undefined method `collect!' for #<Hash:0x00000105178af8>
What could be causing this issue? I can access the url just fine (even using http://example.com/rest/sessions.xml). Is there a way to debug ActiveResource to see what is happening inside?
EDIT
Here is the stack trace:
activeresource (3.0.1) lib/active_resource/base.rb:885:in `instantiate_collection'
activeresource (3.0.1) lib/active_resource/base.rb:857:in `find_every'
activeresource (3.0.1) lib/active_resource/base.rb:777:in `find'
activeresource (3.0.1) lib/active_resource/base.rb:803:in `all'
app/controllers/home_controller.rb:4:in `index'
actionpack (3.0.1) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.0.1) lib/abstract_controller/base.rb:150:in `process_action'
actionpack (3.0.1) lib/action_controller/metal/rendering.rb:11:in `process_action'
actionpack (3.0.1) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (3.0.1) lib/active_support/callbacks.rb:435:in `_run__140584718597918073__process_action__4423897468290757938__callbacks'
activesupport (3.0.1) lib/active_support/callbacks.rb:409:in `_run_process_action_callbacks'
activesupport (3.0.1) lib/active_support/callbacks.rb:93:in `run_callbacks'
actionpack (3.0.1) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.0.1) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.0.1) lib/active_support/notifications.rb:52:in `block in instrument'
activesupport (3.0.1) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.0.1) lib/active_support/notifications.rb:52:in `instrument'
actionpack (3.0.1) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.0.1) lib/action_controller/metal/rescue.rb:17:in `process_action'
actionpack (3.0.1) lib/abstract_controller/base.rb:119:in `process'
actionpack (3.0.1) lib/abstract_controller/rendering.rb:40:in `process'
actionpack (3.0.1) lib/action_controller/metal.rb:133:in `dispatch'
actionpack (3.0.1) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.0.1) lib/action_controller/metal.rb:173:in `block in action'
actionpack (3.0.1) lib/action_dispatch/routing/route_set.rb:62:in `call'
actionpack (3.0.1) lib/action_dispatch/routing/route_set.rb:62:in `dispatch'
actionpack (3.0.1) lib/action_dispatch/routing/route_set.rb:27:in `call'
rack-mount (0.6.13) lib/rack/mount/route_set.rb:148:in `block in call'
rack-mount (0.6.13) lib/rack/mount/code_generation.rb:93:in `block in recognize'
rack-mount (0.6.13) lib/rack/mount/code_generation.rb:68:in `optimized_each'
rack-mount (0.6.13) lib/rack/mount/code_generation.rb:92:in `recognize'
rack-mount (0.6.13) lib/rack/mount/route_set.rb:139:in `call'
actionpack (3.0.1) lib/action_dispatch/routing/route_set.rb:492:in `call'
actionpack (3.0.1) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
actionpack (3.0.1) lib/action_dispatch/middleware/head.rb:14:in `call'
rack (1.2.1) lib/rack/methodoverride.rb:24:in `call'
actionpack (3.0.1) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.0.1) lib/action_dispatch/middleware/flash.rb:182:in `call'
actionpack (3.0.1) lib/action_dispatch/middleware/session/abstract_store.rb:149:in `call'
actionpack (3.0.1) lib/action_dispatch/middleware/cookies.rb:287:in `call'
activerecord (3.0.1) lib/active_record/query_cache.rb:32:in `block in call'
activerecord (3.0.1) lib/active_record/connection_adapters/abstract/query_cache.rb:28:in `cache'
activerecord (3.0.1) lib/active_record/query_cache.rb:12:in `cache'
activerecord (3.0.1) lib/active_record/query_cache.rb:31:in `call'
activerecord (3.0.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:355:in `call'
actionpack (3.0.1) lib/action_dispatch/middleware/callbacks.rb:46:in `block in call'
activesupport (3.0.1) lib/active_support/callbacks.rb:415:in `_run_call_callbacks'
actionpack (3.0.1) lib/action_dispatch/middleware/callbacks.rb:44:in `call'
rack (1.2.1) lib/rack/sendfile.rb:107:in `call'
actionpack (3.0.1) lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
actionpack (3.0.1) lib/action_dispatch/middleware/show_exceptions.rb:46:in `call'
railties (3.0.1) lib/rails/rack/logger.rb:13:in `call'
rack (1.2.1) lib/rack/runtime.rb:17:in `call'
activesupport (3.0.1) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.2.1) lib/rack/lock.rb:11:in `block in call'
<internal:prelude>:10:in `synchronize'
rack (1.2.1) lib/rack/lock.rb:11:in `call'
actionpack (3.0.1) lib/action_dispatch/middleware/static.rb:30:in `call'
railties (3.0.1) lib/rails/application.rb:168:in `call'
railties (3.0.1) lib/rails/application.rb:77:in `method_missing'
railties (3.0.1) lib/rails/rack/log_tailer.rb:14:in `call'
rack (1.2.1) lib/rack/content_length.rb:13:in `call'
rack (1.2.1) lib/rack/handler/webrick.rb:52:in `service'
/Users/swright/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service'
/Users/swright/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run'
/Users/swright/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread'

Answer 1

Simple answer, if you try to session in your views it will access the Rails Session object, you have a naming problem on your hands.
Thats why the Hash error is coming, it tries to access the session Hash.
Try something like
<h1>List Sessions</h1>
<% #sessions.each do |s| %>
<div><%= s.title %></div>
<% end %>
And by the way, you might change your controller to:
class HomeController < ApplicationController
def index
#sessions = Session.all
end
end

Answer 2

For me the problem was the type was not defined in the xml tag
xml.instruct!
xml.posts("type"=>"array") do
#posts.each do |p|
xml.post do
xml.id("type"=>"integer") do
p.id
end
xml.title p.title
xml.content p.content
end
end
end
vs
xml.instruct!
xml.posts do
#posts.each do |p|
xml.post do
xml.id p.id
xml.title p.title
xml.content p.content
end
end
end
Hope this helps you

Answer 3

I had this problem and like Joel above, it was because the type wasn't defined. I found a solution here but briefly if you don't have any control over the XML you can define a custom format, and tell your ActiveResource class to use it:
class TaxAlert < ActiveResource::Base
protected
class CustomFormat
include ActiveResource::Formats::XmlFormat
def decode(xml)
ActiveResource::Formats::XmlFormat.decode(xml)['alert']
end
end
self.format = CustomFormat.new
end