# How does ActiveRecord do it? **URL:** \ **Category:** Ruby\ **Created:** [November 30, 2009, 4:02pm UTC](https://www.ruby-forum.com/t/how-does-activerecord-do-it/179617 "2009-11-30T16:02:56Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\ **Post date:** [November 30, 2009, 4:02pm UTC](https://www.ruby-forum.com/t/how-does-activerecord-do-it/179617/1 "2009-11-30T16:02:56Z")
I know it sounds like a Rails question … but it isn’t. Consider irb(main):001:0\> class X irb(main):002:1\> puts “Hi” irb(main):003:1\> end Hi =\> nil irb(main):004:0\> x = X.new =\> #\ The “Hi” is sent to stdout as the class X is parsed. (Well, after the end statement.) Right? “Hi” is not generated when a new instance of X is created … right? So now consider # in .\app\models\user.rb class X \< ActiveRecord::Base puts “Hi 2” end “Hi 2” gets displayed by webrick every time I generate a form. How does this happen? Is webrick(?) reloading .\app\models\user.rb every time a form is generated? (And now a Rails question …) Assuming it is reloading .\app\models\user.rb in development mode … will it do this in production mode? ---
**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\ **Post date:** [November 30, 2009, 4:31pm UTC](https://www.ruby-forum.com/t/how-does-activerecord-do-it/179617/2 "2009-11-30T16:31:37Z")
On Mon, Nov 30, 2009 at 8:02 AM, Ralph S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Is webrick(?) reloading .\app\models\user.rb every > time a form is generated? Yes, well it’s not webrick doing the reloading, it is Rails, Rails will reload all your models before each request in development mode. Rails configuration API is found here: [http://api.rubyonrails.org/classes/Rails/Configuration.html](http://api.rubyonrails.org/classes/Rails/Configuration.html) In particular the ‘cache\_classes’, attribute which is configured in the RAILS\_ROOT/config/environments/\*.rb filles. You can also review the following files for descriptions of the various options: - RAILS\_ROOT/config/environment.rb - RAILS\_ROOT/config/environments/development.rb - RAILS\_ROOT/config/environments/production.rb - RAILS\_ROOT/config/environments/test.rb > Assuming it is reloading .\app\models\user.rb in development mode … > will it do this in production mode? ‘cache\_classes’ is set to true by default in RAILS\_ROOT/config/environments/production.rb. This disables reloading in production mode. Also, when you’re in the rails console, you can manually reload classes by calling ‘reload!’. The rails mailing list will be able to provide much more satisfactory answers regarding such items in the future. You should post rails related questions there. ---
**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\ **Post date:** [November 30, 2009, 4:52pm UTC](https://www.ruby-forum.com/t/how-does-activerecord-do-it/179617/3 "2009-11-30T16:52:06Z")
MH\> On Mon, Nov 30, 2009 at 8:02 AM, Ralph S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > Is webrick(?) reloading .\app\models\user.rb every > > time a form is generated? MH\> Yes, well it’s not webrick doing the reloading, it is Rails, Rails MH\> will reload all your models before each request in development mode. MH\> Rails configuration API is found here: MH\> [Rails::Configuration](http://api.rubyonrails.org/classes/Rails/Configuration.html) MH\> In particular the ‘cache\_classes’, attribute which is configured in MH\> the RAILS\_ROOT/config/environments/\*.rb filles. You can also review MH\> the following files for descriptions of the various options: MH\> \* RAILS\_ROOT/config/environment.rb MH\> \* RAILS\_ROOT/config/environments/development.rb MH\> \* RAILS\_ROOT/config/environments/production.rb MH\> \* RAILS\_ROOT/config/environments/test.rb > > Assuming it is reloading .\app\models\user.rb in development mode … > > will it do this in production mode? MH\> ‘cache\_classes’ is set to true by default in MH\> RAILS\_ROOT/config/environments/production.rb. This disables reloading MH\> in production mode. MH\> Also, when you’re in the rails console, you can manually reload MH\> classes by calling ‘reload!’. MH\> The rails mailing list will be able to provide much more satisfactory MH\> answers regarding such items in the future. You should post rails MH\> related questions there. The question I was trying to ask was … What _Ruby_ facility does Rails use to reload the class? ---
**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\ **Post date:** [November 30, 2009, 8:41pm UTC](https://www.ruby-forum.com/t/how-does-activerecord-do-it/179617/4 "2009-11-30T20:41:37Z")
> The question I was trying to ask was … > > What _Ruby_ facility does Rails use to reload the class? As a rough answer, Kernel#load and the various const-introspection methods (to remove the old class first). The great thing about open source is that if you’d like a more detailed answer you can just go look at the code and see for yourself. – Markus ---
**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\ **Post date:** [November 30, 2009, 10:39pm UTC](https://www.ruby-forum.com/t/how-does-activerecord-do-it/179617/5 "2009-11-30T22:39:52Z")
On Nov 30, 2009, at 07:51 , Ralph S. wrote: > What _Ruby_ facility does Rails use to reload the class? #load will always load a file (contrasted to #require). Rails does a few other things during reload, but that’s the main mechanism for it.