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::Base
has been evaluated then run_load_hooks
is invoked. The very last line of ActiveRecord::Base
is:
ActiveSupport.run_load_hooks(:active_record, ActiveRecord::Base)
# File activesupport/lib/active_support/lazy_load_hooks.rb, line 41 def on_load(name, options = {}, &block) @loaded[name].each do |base| execute_hook(name, base, options, block) end @load_hooks[name] << [block, options] end
Declares a block that will be executed when a Rails component is fully loaded.
Options:
:yield
- Yields the object that run_load_hooks
to block
.
:run_once
- Given block
will run only once.
# File activesupport/lib/active_support/lazy_load_hooks.rb, line 49 def run_load_hooks(name, base = Object) @loaded[name] << base @load_hooks[name].each do |hook, options| execute_hook(name, base, options, hook) end end
© 2004–2021 David Heinemeier Hansson
Licensed under the MIT License.