diff options
Diffstat (limited to 'activesupport/lib/active_support/lazy_load_hooks.rb')
-rw-r--r-- | activesupport/lib/active_support/lazy_load_hooks.rb | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/lazy_load_hooks.rb b/activesupport/lib/active_support/lazy_load_hooks.rb new file mode 100644 index 0000000000..c23b319046 --- /dev/null +++ b/activesupport/lib/active_support/lazy_load_hooks.rb @@ -0,0 +1,60 @@ +# frozen_string_literal: true + +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 <tt>ActiveRecord::Base</tt> at boot time purely to apply + # configuration. Instead a hook is registered that applies configuration once + # <tt>ActiveRecord::Base</tt> is loaded. Here <tt>ActiveRecord::Base</tt> 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) + 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 + + # Declares a block that will be executed when a Rails component is fully + # loaded. + 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 |