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# frozen_string_literal: true
require "active_support/core_ext/module/delegation"
module ActiveSupport
# NOTE: This approach has been deprecated for end-user code in favor of {thread_mattr_accessor}[rdoc-ref:Module#thread_mattr_accessor] and friends.
# Please use that approach instead.
#
# This module is used to encapsulate access to thread local variables.
#
# Instead of polluting the thread locals namespace:
#
# Thread.current[:connection_handler]
#
# you define a class that extends this module:
#
# module ActiveRecord
# class RuntimeRegistry
# extend ActiveSupport::PerThreadRegistry
#
# attr_accessor :connection_handler
# end
# end
#
# and invoke the declared instance accessors as class methods. So
#
# ActiveRecord::RuntimeRegistry.connection_handler = connection_handler
#
# sets a connection handler local to the current thread, and
#
# ActiveRecord::RuntimeRegistry.connection_handler
#
# returns a connection handler local to the current thread.
#
# This feature is accomplished by instantiating the class and storing the
# instance as a thread local keyed by the class name. In the example above
# a key "ActiveRecord::RuntimeRegistry" is stored in <tt>Thread.current</tt>.
# The class methods proxy to said thread local instance.
#
# If the class has an initializer, it must accept no arguments.
module PerThreadRegistry
def self.extended(object)
object.instance_variable_set :@per_thread_registry_key, object.name.freeze
end
def instance
Thread.current[@per_thread_registry_key] ||= new
end
private
def method_missing(name, *args, &block)
# Caches the method definition as a singleton method of the receiver.
#
# By letting #delegate handle it, we avoid an enclosure that'll capture args.
singleton_class.delegate name, to: :instance
send(name, *args, &block)
end
end
end
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