82 lines
2.5 KiB
Ruby
82 lines
2.5 KiB
Ruby
# frozen_string_literal: true
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module ActiveSupport
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# lazy_load_hooks allows Rails to lazily load a lot of components and thus
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# making the app boot faster. Because of this feature now there is no need to
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# require <tt>ActiveRecord::Base</tt> at boot time purely to apply
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# configuration. Instead a hook is registered that applies configuration once
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# <tt>ActiveRecord::Base</tt> is loaded. Here <tt>ActiveRecord::Base</tt> is
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# used as example but this feature can be applied elsewhere too.
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#
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# Here is an example where +on_load+ method is called to register a hook.
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#
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# initializer 'active_record.initialize_timezone' do
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# ActiveSupport.on_load(:active_record) do
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# self.time_zone_aware_attributes = true
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# self.default_timezone = :utc
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# end
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# end
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#
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# When the entirety of +ActiveRecord::Base+ has been
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# evaluated then +run_load_hooks+ is invoked. The very last line of
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# +ActiveRecord::Base+ is:
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#
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# ActiveSupport.run_load_hooks(:active_record, ActiveRecord::Base)
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module LazyLoadHooks
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def self.extended(base) # :nodoc:
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base.class_eval do
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@load_hooks = Hash.new { |h, k| h[k] = [] }
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@loaded = Hash.new { |h, k| h[k] = [] }
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@run_once = Hash.new { |h, k| h[k] = [] }
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end
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end
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# Declares a block that will be executed when a Rails component is fully
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# loaded.
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#
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# Options:
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#
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# * <tt>:yield</tt> - Yields the object that run_load_hooks to +block+.
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# * <tt>:run_once</tt> - Given +block+ will run only once.
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def on_load(name, options = {}, &block)
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@loaded[name].each do |base|
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execute_hook(name, base, options, block)
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end
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@load_hooks[name] << [block, options]
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end
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def run_load_hooks(name, base = Object)
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@loaded[name] << base
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@load_hooks[name].each do |hook, options|
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execute_hook(name, base, options, hook)
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end
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end
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private
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def with_execution_control(name, block, once)
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unless @run_once[name].include?(block)
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@run_once[name] << block if once
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yield
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end
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end
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def execute_hook(name, base, options, block)
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with_execution_control(name, block, options[:run_once]) do
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if options[:yield]
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block.call(base)
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else
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if base.is_a?(Module)
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base.class_eval(&block)
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else
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base.instance_eval(&block)
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end
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end
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end
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end
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end
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extend LazyLoadHooks
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end
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