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
# File 'activesupport/lib/active_support/current_attributes.rb', line 97
```
[:set, :reset, :resets, :instance, :before_reset, :after_reset, :reset_all, :clear_all]
```
NOT_SET = Internal use only
# File 'activesupport/lib/active_support/current_attributes.rb', line 99
```
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 205


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 201


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

.defaults? ⇒ `Boolean` (rw)

[ GitHub ]

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


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 153


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 115


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 145


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 157


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 169


def current_instances
  ExecutionContext.current_attributes_instances
end

.current_instances_key (private)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 173


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 165


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 103


def instance
  current_instances[current_instances_key] ||= new
end

.method_added(name) (private)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 185


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 177


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 150


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 181


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 209


def attributes
  @attributes.dup
end

#attributes=(value) (rw)

[ GitHub ]

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


attr_writer :attributes

#defaults (readonly)

[ GitHub ]

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


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

#defaults? ⇒ `Boolean` (readonly)

[ GitHub ]

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


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 228


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 223


delegate :set, :reset, to: :instance

Instance Method Details

#resolve_defaults (private)

[ GitHub ]

# File 'activesupport/lib/active_support/current_attributes.rb', line 235


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)