Lazy Load Hooks
LazyLoadHooks
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)
run_load_hooks
will then execute all the hooks that were registered with the on_load
method. In the case of the above example, it will execute the block of code that is in the initializer
.
Registering a hook that has already run results in that hook executing immediately. This allows hooks to be nested for code that relies on multiple lazily loaded components:
initializer "action_text.renderer" do
ActiveSupport.on_load(:action_controller_base) do
ActiveSupport.on_load(:action_text_content) do
self.default_renderer = Class.new(ActionController::Base).renderer
end
end
end
Instance Public methods
on_load(name, options = {}, &block) Link
Declares a block that will be executed when a Rails component is fully loaded. If the component has already loaded, the block is executed immediately.
Options:
-
:yield
- Yields the object thatrun_load_hooks
toblock
. -
:run_once
- Givenblock
will run only once.
run_load_hooks(name, base = Object) Link
Executes all blocks registered to name
via on_load
, using base
as the evaluation context.
ActiveSupport.run_load_hooks(:active_record, ActiveRecord::Base)
In the case of the above example, it will execute all hooks registered for :active_record
within the class ActiveRecord::Base
.