Class: ActiveSupport::CurrentAttributes

Inherits:
Object
  • Object
show all
Includes:
Callbacks
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. = user.
  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..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.

Direct Known Subclasses

ActiveStorage::Current

Defined Under Namespace

Modules: TestHelper

Constant Summary collapse

INVALID_ATTRIBUTE_NAMES =

:nodoc:

[:set, :reset, :resets, :instance, :before_reset, :after_reset, :reset_all, :clear_all]
NOT_SET =

:nodoc:

Object.new.freeze

Constants included from Callbacks

ActiveSupport::Callbacks::CALLBACK_FILTER_TYPES

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Callbacks

#run_callbacks

Methods included from Concern

#append_features, #class_methods, extended, #included, #prepend_features, #prepended

Constructor Details

#initialize ⇒ CurrentAttributes

Returns a new instance of CurrentAttributes.



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

def initialize
  @attributes = resolve_defaults
end

Instance Attribute Details

#attributes ⇒ Object

Returns the value of attribute attributes.



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# File 'activesupport/lib/active_support/current_attributes.rb', line 197

def attributes
  @attributes
end

Class Method Details

.attribute(*names, default: NOT_SET) ⇒ Object

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.


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# 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

.before_reset(*methods, &block) ⇒ Object

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



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# File 'activesupport/lib/active_support/current_attributes.rb', line 144

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

.clear_all ⇒ Object

:nodoc:



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# File 'activesupport/lib/active_support/current_attributes.rb', line 160

def clear_all # :nodoc:
  reset_all
  current_instances.clear
end

.instance ⇒ Object

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



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# File 'activesupport/lib/active_support/current_attributes.rb', line 102

def instance
  current_instances[current_instances_key] ||= new
end

.reset_all ⇒ Object

:nodoc:



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# File 'activesupport/lib/active_support/current_attributes.rb', line 156

def reset_all # :nodoc:
  current_instances.each_value(&:reset)
end

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

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



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# File 'activesupport/lib/active_support/current_attributes.rb', line 149

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

Instance Method Details

#reset ⇒ Object

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



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# File 'activesupport/lib/active_support/current_attributes.rb', line 218

def reset
  run_callbacks :reset do
    self.attributes = resolve_defaults
  end
end

#set(attributes, &block) ⇒ Object

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


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# File 'activesupport/lib/active_support/current_attributes.rb', line 213

def set(attributes, &block)
  with(**attributes, &block)
end