module ActiveSupport # lazy_load_hooks allows Rails to lazily load a lot of components and thus # making the app boot faster. Because of this feature now there is no need to # require ActiveRecord::Base at boot time purely to apply # configuration. Instead a hook is registered that applies configuration once # ActiveRecord::Base is loaded. Here ActiveRecord::Base is # used as example but this feature can be applied elsewhere too. # # Here is an example where +on_load+ method is called to register a hook. # # initializer 'active_record.initialize_timezone' do # ActiveSupport.on_load(:active_record) do # self.time_zone_aware_attributes = true # self.default_timezone = :utc # end # end # # When the entirety of +activerecord/lib/active_record/base.rb+ has been # evaluated then +run_load_hooks+ is invoked. The very last line of # +activerecord/lib/active_record/base.rb+ is: # # ActiveSupport.run_load_hooks(:active_record, ActiveRecord::Base) module LazyLoadHooks def self.extended(base) # :nodoc: base.class_eval do @load_hooks = Hash.new { |h,k| h[k] = [] } @loaded = Hash.new { |h,k| h[k] = [] } end end def on_load(name, options = {}, &block) @loaded[name].each do |base| execute_hook(base, options, block) end @load_hooks[name] << [block, options] end def execute_hook(base, options, block) if options[:yield] block.call(base) else base.instance_eval(&block) end end def run_load_hooks(name, base = Object) @loaded[name] << base @load_hooks[name].each do |hook, options| execute_hook(base, options, hook) end end end extend LazyLoadHooks end