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)
# File activesupport/lib/active_support/lazy_load_hooks.rb, line 39 def execute_hook(base, options, block) if options[:yield] block.call(base) else base.instance_eval(&block) end end
# File activesupport/lib/active_support/lazy_load_hooks.rb, line 31 def on_load(name, options = {}, &block) @loaded[name].each do |base| execute_hook(base, options, block) end @load_hooks[name] << [block, options] end
# File activesupport/lib/active_support/lazy_load_hooks.rb, line 47 def run_load_hooks(name, base = Object) @loaded[name] << base @load_hooks[name].each do |hook, options| execute_hook(base, options, hook) end end
© 2004–2017 David Heinemeier Hansson
Licensed under the MIT License.