# Rails class cacheing in development mode **URL:** \ **Category:** Rails\ **Created:** [March 30, 2009, 7:23pm UTC](https://www.ruby-forum.com/t/rails-class-cacheing-in-development-mode/164273 "2009-03-30T19:23:23Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![interactivenyc](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/85f322/32.png) [@interactivenyc](https://www.ruby-forum.com/u/interactivenyc)\ **Post date:** [March 30, 2009, 7:23pm UTC](https://www.ruby-forum.com/t/rails-class-cacheing-in-development-mode/164273/1 "2009-03-30T19:23:23Z")
I have a rails application that patches ActiveRecord with a hand-coded validator. The patch is made by adding the following lines in config/ environment.rb Rails::Initializer.run do |config| … end class ActiveRecord::Base include MtLib::DBValidations end This works fine in production mode i.e. with config.cache\_classes = true however it does not work in development with cache\_classes set to false. The error thrown is ``` ArgumentError (A copy of MtLib::DBValidations has been removed ``` from the module tree but is still active!): My question is what is the process that is followed when cache\_class is set to false. Does Rails re-run any of the initialization methods? If not then where is the best place for me to put my patch to ensure that it is in all models and survives a classes reload? I have tried adding the patch to config/initializers/ active\_record\_patch, however this is not re-run when the classes are reloaded. ---
**Author:** ![interactivenyc](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/85f322/32.png) [@interactivenyc](https://www.ruby-forum.com/u/interactivenyc)\ **Post date:** [March 30, 2009, 7:25pm UTC](https://www.ruby-forum.com/t/rails-class-cacheing-in-development-mode/164273/2 "2009-03-30T19:25:44Z")
On Mar 30, 6:20 pm, sweet61 [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > It doesn’t rerun any initialization. If you add your file to ActiveSupport::Dependencies.load\_once\_paths then it won’t get unloaded. Fred ---
**Author:** ![interactivenyc](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/85f322/32.png) [@interactivenyc](https://www.ruby-forum.com/u/interactivenyc)\ **Post date:** [March 30, 2009, 8:13pm UTC](https://www.ruby-forum.com/t/rails-class-cacheing-in-development-mode/164273/3 "2009-03-30T20:13:49Z")
Thanks Frederick, That worked perfectly. I modified environment.rb as follows :- config.load\_paths += %W( #{RAILS\_ROOT}/lib/soap\_clients/company # {RAILS\_ROOT}/lib/mt\_lib) # Make sure load\_once\_paths is a subset of load\_paths config.load\_once\_paths += %W( #{RAILS\_ROOT}/lib/mt\_lib) On Mar 30, 6:24 pm, Frederick C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![interactivenyc](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/85f322/32.png) [@interactivenyc](https://www.ruby-forum.com/u/interactivenyc)\ **Post date:** [March 30, 2009, 10:01pm UTC](https://www.ruby-forum.com/t/rails-class-cacheing-in-development-mode/164273/4 "2009-03-30T22:01:13Z")
Sorry Frederick. This issue is partly resolved but not quite. The problem I think is that I am patching ActiveRecord during initialization. I have stopped my validation code from being unloaded, however when activerecord is reloaded, or particularly my models then they are no longer patched. Does that sound reasonable? Is there some way I can patch ActiveRecord so it will be patched again when the class is reloaded? Of course I may be totally off-base here and the problem is down to the way ActionWebService is reloading classes, as the model classes are being used within ActionWebService and it is this that is throwing the exception. Steve ---
**Author:** ![interactivenyc](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/85f322/32.png) [@interactivenyc](https://www.ruby-forum.com/u/interactivenyc)\ **Post date:** [March 30, 2009, 10:38pm UTC](https://www.ruby-forum.com/t/rails-class-cacheing-in-development-mode/164273/5 "2009-03-30T22:38:09Z")
On Mar 30, 9:00 pm, sweet61 [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Sorry Frederick. This issue is partly resolved but not quite. > > The problem I think is that I am patching ActiveRecord during > initialization. I have stopped my validation code from being unloaded, > however when activerecord is reloaded, or particularly my models then > they are no longer patched. Does that sound reasonable? > > Is there some way I can patch ActiveRecord so it will be patched again > when the class is reloaded? ActiveRecord isn’t reloaded ever - only your code is reloaded (which is problematic in your initial case because). Unless you were doing something particularly funky I’m not sure off the top of my head what would be wrong. > Of course I may be totally off-base here and the problem is down to > the way ActionWebService is reloading classes, as the model classes > are being used within ActionWebService and it is this that is throwing > the exception. Don’t think that has anything to do with that - the reloading stuff is just part of the general request lifecycle stufff. Fred ---
**Author:** ![interactivenyc](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/85f322/32.png) [@interactivenyc](https://www.ruby-forum.com/u/interactivenyc)\ **Post date:** [March 31, 2009, 12:33am UTC](https://www.ruby-forum.com/t/rails-class-cacheing-in-development-mode/164273/6 "2009-03-31T00:33:34Z")
When you say, “Unless I’m doing something particularly funky”, well… I have a hand-rolled validator that validates my models based upon the company that is submitting the data and the country they are in. This validator internally uses it’s own active-record models to hold the validation data, so it has models called Model, Field, FieldItems etc. I now understand that ActiveRecord is never reloaded, however my validation models are presumably unloaded. This leaves my validation module loaded but it’s internally used models are unloaded. Does this explain the behaviour I am seeing and is there a way around it? On Mar 30, 9:37 pm, Frederick C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)