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 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/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)

The TimeZone class serves as a wrapper around TZInfo::Timezone instances. It allows us to do the following:

Limit the set of zones provided by TZInfo to a meaningful subset of 142 zones.
Retrieve and display zones with a friendlier name (e.g., “Eastern Time (US & Canada)” instead of “America/New_York”).
Lazily load TZInfo::Timezone instances only when they’re needed.
Create ActiveSupport::TimeWithZone instances via TimeZone’s local, parse, at and now methods.

If you set config.time_zone in the Rails Application, you can access this TimeZone object via Time.zone:

# application.rb:
class Application < Rails::Application
  config.time_zone = "Eastern Time (US & Canada)"
end

Time.zone       # => #<TimeZone:0x514834...>
Time.zone.name  # => "Eastern Time (US & Canada)"
Time.zone.now   # => Sun, 18 May 2008 14:30:44 EDT -04:00

The version of TZInfo bundled with Active Support only includes the definitions necessary to support the zones defined by the TimeZone class. If you need to use zones that aren’t defined by TimeZone, you’ll need to install the TZInfo gem (if a recent version of the gem is installed locally, this will be used instead of the bundled version.)

This class has dubious semantics and we only have it so that people can write params[:key] instead of params['key'] and they get the same value for both keys.

Some code from jeremymcanally’s “pending” github.com/jeremymcanally/pending/tree/master

XmlMini LibXML implementation using a SAX-based parser

XmlMini Nokogiri implementation

XmlMini Nokogiri implementation using a SAX-based parser

XmlMini ReXML implementation

XmlMini JRuby JDOM implementation

XmlMini LibXML implementation

Attributes

load_all_hooks[RW]

Public Class Methods

execute_hook(base, options, block) click to toggle source

# File lib/active_support/lazy_load_hooks.rb, line 32
def self.execute_hook(base, options, block)
  if options[:yield]
    block.call(base)
  else
    base.instance_eval(&block)
  end
end

load_all!() click to toggle source

# File lib/active_support.rb, line 30
def load_all!; load_all_hooks.each { |hook| hook.call } end

on_load(name, options = {}, &block) click to toggle source

# File lib/active_support/lazy_load_hooks.rb, line 24
def self.on_load(name, options = {}, &block)
  if base = @loaded[name]
    execute_hook(base, options, block)
  else
    @load_hooks[name] << [block, options]
  end
end

on_load_all(&hook) click to toggle source

# File lib/active_support.rb, line 29
def on_load_all(&hook) load_all_hooks << hook end

run_load_hooks(name, base = Object) click to toggle source

# File lib/active_support/lazy_load_hooks.rb, line 40
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

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