Class: ActiveSupport::CurrentAttributes

Relationships & Source Files
Namespace Children
Modules: `TestHelper`
Super Chains via Extension / Inclusion / Inheritance
Class Chain: self, `DescendantsTracker`
Instance Chain: self, `Callbacks`
Inherits:	Object
Defined in:	activesupport/lib/active_support/current_attributes.rb

Overview

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.

Constant Summary

INVALID_ATTRIBUTE_NAMES = Internal use only

Declaring an attribute by one of these names would shadow the methods CurrentAttributes itself relies on. Computed at the very end of the class body so that all the methods defined above are captured.

# File 'activesupport/lib/active_support/current_attributes.rb', line 244
```
(methods(false) + private_methods(false) + instance_methods(false) + private_instance_methods(false)).uniq.sort.freeze
```
NOT_SET = Internal use only
# File 'activesupport/lib/active_support/current_attributes.rb', line 97
```
Object.new.freeze
```

`Callbacks` - Included

CALLBACK_FILTER_TYPES

`Callbacks` - Attributes & Methods

.__callbacks rw
#__callbacks readonly

Class Method Summary

.after_reset(*methods, &block)

Alias for .resets.
.attribute(*names, default: NOT_SET)

Declares one or more attributes that will be given both class and instance accessor methods.
.before_reset(*methods, &block)

Calls this callback before #reset is called on the instance.
.instance

Returns singleton instance for this class in this thread.
.new ⇒ CurrentAttributes constructor
.resets(*methods, &block) (also: .after_reset)

Calls this callback after #reset is called on the instance.
.current_instances private
.current_instances_key private
.generated_attribute_methods private
.method_added(name) private
.method_missing(name) private
.respond_to_missing?(name, _) ⇒ Boolean private
.clear_all Internal use only

`DescendantsTracker` - self

descendants, subclasses, clear, disable_clear!, reject!

Instance Attribute Summary

#attributes rw
#attributes=(value) rw
#defaults readonly
#defaults? ⇒ Boolean readonly
#reset readonly

Reset all attributes.
#set(attributes, &block) readonly

Expose one or more attributes within a block.

Instance Method Summary

#resolve_defaults private

`Callbacks` - Included

#run_callbacks	Runs the callbacks for the given event.
#halted_callback_hook	A hook invoked every time a before callback is halted.

Constructor Details

.new ⇒ `CurrentAttributes`

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 203


def initialize
  @attributes = resolve_defaults
end

Class Attribute Details

.__callbacks (rw)

[ GitHub ]

# File 'activesupport/lib/active_support/callbacks.rb', line 70


class_attribute :__callbacks, instance_writer: false, instance_predicate: false, default: {}

.defaults (rw)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 199


class_attribute :defaults, instance_writer: false, default: {}.freeze

.defaults? ⇒ `Boolean` (rw)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 199


class_attribute :defaults, instance_writer: false, default: {}.freeze

Class Method Details

.after_reset(*methods, &block)

Alias for .resets.

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 151


alias_method :after_reset, :resets

.attribute(*names, default: NOT_SET)

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.

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 113


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

  Delegation.generate(singleton_class, names, to: :instance, nilable: false, signature: "")
  Delegation.generate(singleton_class, names.map { |n| "#{n}=" }, to: :instance, nilable: false, signature: "value")

  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

  self.defaults = defaults.merge(names.index_with { default })
end

.before_reset(*methods, &block)

Calls this callback before #reset is called on the instance. Used for resetting external collaborators that depend on current values.

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 143


def before_reset(*methods, &block)
  set_callback :reset, :before, *methods, &block
end

.clear_all

This method is for internal use only.

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 155


def clear_all # :nodoc:
  if instances = current_instances
    instances.values.each(&:reset)
    instances.clear
  end
end

.current_instances (private)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 167


def current_instances
  ExecutionContext.current_attributes_instances
end

.current_instances_key (private)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 171


def current_instances_key
  @current_instances_key ||= name.to_sym
end

.generated_attribute_methods (private)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 163


def generated_attribute_methods
  @generated_attribute_methods ||= Module.new.tap { |mod| include mod }
end

.instance

Returns singleton instance for this class in this thread. If none exists, one is created.

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 101


def instance
  current_instances[current_instances_key] ||= new
end

.method_added(name) (private)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 183


def method_added(name)
  super

  # We try to generate instance delegators early to not rely on method_missing.
  return if name == :initialize

  # If the added method isn't public, we don't delegate it.
  return unless public_method_defined?(name)

  # If we already have a class method by that name, we don't override it.
  return if singleton_class.method_defined?(name) || singleton_class.private_method_defined?(name)

  Delegation.generate(singleton_class, [name], to: :instance, as: self, nilable: false)
end

.method_missing(name) (private)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 175


def method_missing(name, ...)
  instance.public_send(name, ...)
end

.resets(*methods, &block) Also known as: .after_reset

Calls this callback after #reset is called on the instance. Used for resetting external collaborators, like Time.zone.

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 148


def resets(*methods, &block)
  set_callback :reset, :after, *methods, &block
end

.respond_to_missing?(name, _) ⇒ `Boolean` (private)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 179


def respond_to_missing?(name, _)
  instance.respond_to?(name) || super
end

Instance Attribute Details

#__callbacks (readonly)

[ GitHub ]

# File 'activesupport/lib/active_support/callbacks.rb', line 70


class_attribute :__callbacks, instance_writer: false, instance_predicate: false, default: {}

#attributes (rw)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 207


def attributes
  @attributes.dup
end

#attributes=(value) (rw)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 201


attr_writer :attributes

#defaults (readonly)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 199


class_attribute :defaults, instance_writer: false, default: {}.freeze

#defaults? ⇒ `Boolean` (readonly)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 199


class_attribute :defaults, instance_writer: false, default: {}.freeze

#reset (readonly)

Reset all attributes. Should be called before and after actions, when used as a per-request singleton.

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 226


delegate :set, :reset, to: :instance

#set(attributes, &block) (readonly)

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

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 221


delegate :set, :reset, to: :instance

Instance Method Details

#resolve_defaults (private)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 233


def resolve_defaults
  defaults.each_with_object({}) do |(key, value), result|
    if value != NOT_SET
      result[key] = Proc === value ? value.call : value.dup
    end
  end
end

Class: ActiveSupport::CurrentAttributes

Overview

Current Attributes

Constant Summary

Callbacks - Included

Callbacks - Attributes & Methods

Class Attribute Summary

Class Method Summary

DescendantsTracker - self

Instance Attribute Summary

Instance Method Summary

Callbacks - Included

Constructor Details

.new ⇒ CurrentAttributes

Class Attribute Details

.__callbacks (rw)

.defaults (rw)

.defaults? ⇒ Boolean (rw)

Class Method Details

.after_reset(*methods, &block)

.attribute(*names, default: NOT_SET)

Options

.before_reset(*methods, &block)

.clear_all

.current_instances (private)

.current_instances_key (private)

.generated_attribute_methods (private)

.instance

.method_added(name) (private)

.method_missing(name) (private)

.resets(*methods, &block) Also known as: .after_reset

.respond_to_missing?(name, _) ⇒ Boolean (private)

Instance Attribute Details

#__callbacks (readonly)

#attributes (rw)

#attributes=(value) (rw)

#defaults (readonly)

#defaults? ⇒ Boolean (readonly)

#reset (readonly)

#set(attributes, &block) (readonly)

Instance Method Details

#resolve_defaults (private)

`Callbacks` - Included

`Callbacks` - Attributes & Methods

`DescendantsTracker` - self

`Callbacks` - Included

.new ⇒ `CurrentAttributes`

.defaults? ⇒ `Boolean` (rw)

.respond_to_missing?(name, _) ⇒ `Boolean` (private)

#defaults? ⇒ `Boolean` (readonly)