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 Thread.current. # 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 protected def method_missing(name, *args, &block) # :nodoc: # 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