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Class: ActiveSupport::CurrentAttributes

Relationships & Source Files
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 :, :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.

Constant Summary

Callbacks - Included

CALLBACK_FILTER_TYPES

Callbacks - Attributes & Methods

Class Method Summary

DescendantsTracker - self

descendants

See additional method definition at line 104.
subclasses

See additional method definition at line 100.

Instance Attribute Summary

Instance Method Summary

Callbacks - Included

#run_callbacks

Runs the callbacks for the given event.

Constructor Details

.new ⇒ CurrentAttributes

[ GitHub ] 

  


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



def initialize
  @attributes = {}
end


  







Class Attribute Details



  

    .__callbacks   (rw)
  

  [ GitHub ]


  

  


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



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


  








  

    .__callbacks?  ⇒ Boolean  (rw)
  

  [ GitHub ]


  

  


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



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


  







Class Method Details



  

    .after_reset(*methods, &block)  
  



  

    

Alias for .resets.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/current_attributes.rb', line 154



alias_method :after_reset, :resets


  








  

    .attribute(*names)  
  



  

    

Declares one or more attributes that will be given both class and instance accessor methods.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/current_attributes.rb', line 104



def attribute(*names)
  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

  ActiveSupport::CodeGenerator.batch(singleton_class, __FILE__, __LINE__) do |owner|
    names.each do |name|
      owner.define_cached_method(name, namespace: :current_attributes_delegation) do |batch|
        batch <<
          "def #{name}" <<
          "instance.#{name}" <<
          "end"
      end
      owner.define_cached_method("#{name}=", namespace: :current_attributes_delegation) do |batch|
        batch <<
          "def #{name}=(value)" <<
          "instance.#{name} = value" <<
          "end"
      end
    end
  end
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 146



def before_reset(*methods, &block)
  set_callback :reset, :before, *methods, &block
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 99



def instance
  current_instances[current_instances_key] ||= new
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 151



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


  







Instance Attribute Details



  

    #__callbacks   (readonly)
  

  [ GitHub ]


  

  


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



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


  








  

    #__callbacks?  ⇒ Boolean  (readonly)
  

  [ GitHub ]


  

  


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



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


  








  

    #attributes   (rw)
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/current_attributes.rb', line 195



attr_accessor :attributes


  








  

    #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 220



delegate :set, :reset, to: :instance


  








  

    #set(set_attributes)   (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 211



delegate :set, :reset, to: :instance