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# 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/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 ActiveSupport
@load_hooks = Hash.new { |h,k| h[k] = [] }
@loaded = Hash.new { |h,k| h[k] = [] }
def self.on_load(name, options = {}, &block)
@loaded[name].each do |base|
execute_hook(base, options, block)
end
@load_hooks[name] << [block, options]
end
def self.execute_hook(base, options, block)
if options[:yield]
block.call(base)
else
base.instance_eval(&block)
end
end
def self.run_load_hooks(name, base = Object)
@loaded[name] << base
@load_hooks[name].each do |hook, options|
execute_hook(base, options, hook)
end
end
end
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