undefined method `<=>' error

[feurio]

For most parts of my rails application cache-money works really nice.

But how do I solve this error. Without cache-money I do not have this error:
(Is there a way to disable cache-money for a certain model?)

NoMethodError (undefined method <=>' for #<UserActivity:0x1072c9b58>): /Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/index.rb:124:inadd_object_to_cache'
/Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/index.rb:123:in sort' /Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/index.rb:123:inadd_object_to_cache'
/Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/index.rb:161:in update_index_with_minimal_network_operations' /Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/index.rb:31:inupdate'
/Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/write_through.rb:60:in update_caches' /Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/write_through.rb:60:ineach'
/Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/write_through.rb:60:in update_caches' /Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/write_through.rb:48:insend'
/Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/write_through.rb:48:in unfold' /Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/write_through.rb:26:inupdate_caches'
/Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cache_money.rb:52:in transaction_without_trace_ActiveRecord_self_name_transaction' /Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/transactional.rb:13:intransaction'
/Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cache_money.rb:52:in transaction_without_trace_ActiveRecord_self_name_transaction' /Library/Ruby/Gems/1.8/gems/newrelic_rpm-2.12.3/lib/new_relic/agent/method_tracer.rb:319:intransaction'
/Library/Ruby/Gems/1.8/gems/newrelic_rpm-2.12.3/lib/new_relic/agent/method_tracer.rb:141:in trace_execution_scoped' /Library/Ruby/Gems/1.8/gems/newrelic_rpm-2.12.3/lib/new_relic/agent/method_tracer.rb:314:intransaction'
app/models/user_activity.rb:126:in generate_html' app/models/user_activity.rb:108:increate_html'
/Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cache_money.rb:52:in transaction_without_trace_ActiveRecord_self_name_transaction' /Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cash/transactional.rb:13:intransaction'
/Library/Ruby/Gems/1.8/gems/af-cache-money-0.2.10/lib/cache_money.rb:52:in transaction_without_trace_ActiveRecord_self_name_transaction' /Library/Ruby/Gems/1.8/gems/newrelic_rpm-2.12.3/lib/new_relic/agent/method_tracer.rb:319:intransaction'
/Library/Ruby/Gems/1.8/gems/newrelic_rpm-2.12.3/lib/new_relic/agent/method_tracer.rb:141:in trace_execution_scoped' /Library/Ruby/Gems/1.8/gems/newrelic_rpm-2.12.3/lib/new_relic/agent/method_tracer.rb:314:intransaction'
app/models/activity.rb:151:in `log'

[guilleiguaran]

I have same bug, maybe it ocurrs in a callback?

[dmilith]

same here. Even after removing c-m indices from model! Please help.

[guilleiguaran]

You must define <=> for ActiveRecord::Base, i do it in cache_money initializer:

 class ActiveRecord::Base
   is_cached :repository => $cache
   def <=>(other)
      self.id <=> other.id
   end
 end