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/Ruby on Rails 5.2

module ActiveSupport::PerThreadRegistry

NOTE: This approach has been deprecated for end-user code in favor of 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.

Public Class Methods

extended(object) Show source
# File activesupport/lib/active_support/per_thread_registry.rb, line 42
def self.extended(object)
  object.instance_variable_set "@per_thread_registry_key", object.name.freeze
end

Public Instance Methods

instance() Show source
# File activesupport/lib/active_support/per_thread_registry.rb, line 46
def instance
  Thread.current[@per_thread_registry_key] ||= new
end

© 2004–2018 David Heinemeier Hansson
Licensed under the MIT License.