ActiveSupport Configurable
ActiveSupport::Configurable let us store options with ActiveSupport::OrderHash(Ruby1.8 is undefined, 1.9 did) in a class or object. Let' see how we can do that:
require "active_support/configurable"
class Witch
include ActiveSupport::Configurable
config_accessor :weapon, :instance_reader => true, :instance_writer => false
config_accessor :helmet, :instance_reader => false, :instance_writer => true
# initialize config block
configure do |c|
c.weapon = 'Fire Truncheon'
c.helmet = 'Iron Helmet +1'
end
end
With'config'hash, we can edit options at will in class or instance.
config_accessorallows you to add shortcut so that you don't have to refer to attribute through config.
instance_readerandinstance_writermake objects can read and write the attribute.From above code, Witchclass and objects haveweaponandhelmetattributes:
Witch.config
#{:weapon=>"Fire Truncheon", :helmet=>"Iron Helmet +1", :ring=>"Ice ring"}
Witch.config.weapon = "Truncheon"
#{:weapon=>"Truncheon", :helmet=>"Iron Helmet +1", :ring=>"Ice ring"}
Witch.new.config.weapon = "Truncheon +10"
Witch.weapon #Fire Truncheon
Witch.helmet #Iron Helmet +1
john = Witch.new
john.weapon #Fire Truncheon
john.weapon = "Royal Truncheon +1"
#activesupport_configurable.rb:26:in `<main>':
#undefined method `weapon=' for #<Witch:0x94136ac @_config={}> (NoMethodError)
john.helmet = "Normal Helmet"
john.helmet #Normal Helmet
#helmet have no reader method
john.helmet
#activesupport_configurable.rb:30:in `<main>':
#undefined method `helmet' for #<Witch:0x9999cac @_config={:weapon=>"Royal Truncheon +1"}> (NoMethodError)
Inside the source code
reader, line = "def #{name}; config.#{name}; end", __LINE__
writer, line = "def #{name}=(value); config.#{name} = value; end", __LINE__
class_eval reader, __FILE__, line unless options[:instance_reader] == false
class_eval writer, __FILE__, line unless options[:instance_writer] == false
we can see that it adds reader and writer instance methods to the class by class_eval,