class ActiveSupport::CurrentAttributes
Current Attributes
Abstract super class that provides a thread-isolated attributes singleton, which resets automatically before and after each request. This allows you to keep all the per-request attributes easily available to the whole system.
The following full app-like example demonstrates how to use a Current class to facilitate easy access to the global, per-request attributes without passing them deeply around everywhere:
# app/models/current.rb
class Current < ActiveSupport::CurrentAttributes
attribute :account, :user
attribute :request_id, :user_agent, :ip_address
resets { Time.zone = nil }
def user=(user)
super
self.account = user.account
Time.zone = user.time_zone
end
end
# app/controllers/concerns/authentication.rb
module Authentication
extend ActiveSupport::Concern
included do
before_action :authenticate
end
private
def authenticate
if authenticated_user = User.find_by(id: cookies.encrypted[:user_id])
Current.user = authenticated_user
else
redirect_to new_session_url
end
end
end
# app/controllers/concerns/set_current_request_details.rb
module SetCurrentRequestDetails
extend ActiveSupport::Concern
included do
before_action do
Current.request_id = request.uuid
Current.user_agent = request.user_agent
Current.ip_address = request.ip
end
end
end
class ApplicationController < ActionController::Base
include Authentication
include SetCurrentRequestDetails
end
class MessagesController < ApplicationController
def create
Current.account.messages.create(message_params)
end
end
class Message < ApplicationRecord
belongs_to :creator, default: -> { Current.user }
after_create { |message| Event.create(record: message) }
end
class Event < ApplicationRecord
before_create do
self.request_id = Current.request_id
self.user_agent = Current.user_agent
self.ip_address = Current.ip_address
end
end
A word of caution: It’s easy to overdo a global singleton like Current and tangle your model as a result. Current should only be used for a few, top-level globals, like account, user, and request details. The attributes stuck in Current should be used by more or less all actions on all requests. If you start sticking controller-specific attributes in there, you’re going to create a mess.
Inherits From
-
module
ActiveSupport::
Callbacks
Attributes
[RW] | attributes |
Public class methods
Alias for:
resets
.
Declares one or more attributes that will be given both class and instance accessor methods.
Options
-
:default
- The default value for the attributes. If the value
is a proc or lambda, it will be called whenever an instance is constructed. Otherwise, the value will be duplicated with #dup
. Default values are re-assigned when the attributes are reset.
Source code GitHub
# File activesupport/lib/active_support/current_attributes.rb, line 114
def attribute(*names, default: NOT_SET)
invalid_attribute_names = names.map(&:to_sym) & INVALID_ATTRIBUTE_NAMES
if invalid_attribute_names.any?
raise ArgumentError, "Restricted attribute names: #{invalid_attribute_names.join(", ")}"
end
ActiveSupport::CodeGenerator.batch(generated_attribute_methods, __FILE__, __LINE__) do |owner|
names.each do |name|
owner.define_cached_method(name, namespace: :current_attributes) do |batch|
batch <<
"def #{name}" <<
"attributes[:#{name}]" <<
"end"
end
owner.define_cached_method("#{name}=", namespace: :current_attributes) do |batch|
batch <<
"def #{name}=(value)" <<
"attributes[:#{name}] = value" <<
"end"
end
end
end
Delegation.generate(singleton_class, names, to: :instance, nilable: false, signature: "")
Delegation.generate(singleton_class, names.map { |n| "#{n}=" }, to: :instance, nilable: false, signature: "value")
self.defaults = defaults.merge(names.index_with { default })
end
Calls this callback before reset
is called on the instance. Used for resetting external collaborators that depend on current values.
Source code GitHub
# File activesupport/lib/active_support/current_attributes.rb, line 144
def before_reset(*methods, &block)
set_callback :reset, :before, *methods, &block
end
Returns singleton instance for this class in this thread. If none exists, one is created.
Source code GitHub
# File activesupport/lib/active_support/current_attributes.rb, line 102
def instance
current_instances[current_instances_key] ||= new
end
Source code GitHub
# File activesupport/lib/active_support/current_attributes.rb, line 199
def initialize
@attributes = resolve_defaults
end
Also aliased as:
after_reset
.
Calls this callback after reset
is called on the instance. Used for resetting external collaborators, like Time.zone
.
Source code GitHub
# File activesupport/lib/active_support/current_attributes.rb, line 149
def resets(*methods, &block)
set_callback :reset, :after, *methods, &block
end
Public instance methods
Reset all attributes. Should be called before and after actions, when used as a per-request singleton.
Source code GitHub
# File activesupport/lib/active_support/current_attributes.rb, line 218
def reset
run_callbacks :reset do
self.attributes = resolve_defaults
end
end
Expose one or more attributes within a block. Old values are returned after the block concludes. Example demonstrating the common use of needing to set Current attributes outside the request-cycle:
class Chat::PublicationJob < ApplicationJob
def perform(attributes, room_number, creator)
Current.set(person: creator) do
Chat::Publisher.publish(attributes: attributes, room_number: room_number)
end
end
end
Source code GitHub
# File activesupport/lib/active_support/current_attributes.rb, line 213
def set(attributes, &block)
with(**attributes, &block)
end