Lazy Load Hooks

Lazy Load Hooks

Commit e58e3faf introduces the notion of lazy load hooks as provided by ActiveSupport.

Read here for more information on how to use them

• http://www.simonecarletti.com/blog/2011/04/understanding-ruby-and-rails-lazy-load-hooks/
• https://github.com/rails/rails/blob/c0a5b8505d0fa9095cbee8b709f9aadf630a3716/activesupport/lib/active_support/lazy_load_hooks.rb

If you are developing a plugin and need to register some code to run after a particular model has loaded you can register a load hook.

E.g. Fat Free CRM uses this feature to load the settings file after the Setting class is invoked.

ActiveSupport.on_load(:fat_free_crm_setting) do

  setting_files = [FatFreeCRM.root.join("config", "settings.default.yml")]
  setting_files << Rails.root.join("config", "settings.yml") unless Rails.env == 'test'
  setting_files.each do |settings_file|
    Setting.load_settings_from_yaml(settings_file) if File.exist?(settings_file)
  end

end

(Taken from https://github.com/fatfreecrm/fat_free_crm/blob/master/lib/fat_free_crm/load_settings.rb)

The last line of https://github.com/fatfreecrm/fat_free_crm/blob/master/app/models/setting.rb#L118 class activates the hook.

ActiveSupport.run_load_hooks(:fat_free_crm_setting, self)

This can also be used in plugins. Say, for example, you want to register your own custom field. You can configure your engine.rb as such:

config.to_prepare do
  ActiveSupport.on_load(:fat_free_crm_field) do
    self.register(:as => 'example', :klass => 'CustomFieldExample', :type => 'string')
  end
end

This will be triggered when the 'fat_free_crm_field' hook is run. This happens immediately after the Field class is loaded.

Hooks have been placed on all models in the app/models directory. Take a look at the last line of each specific model for the name of the hook to register. They follow the "fat_free_crm_classname" convention.