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module ActiveRecord::SignedId::ClassMethods

Public instance methods

Lets you find a record based on a signed id that’s safe to put into the world without risk of tampering. This is particularly useful for things like password reset or email verification, where you want the bearer of the signed id to be able to interact with the underlying record, but usually only within a certain time period.

You set the time period that the signed id is valid for during generation, using the instance method signed_id(expires_in: 15.minutes). If the time has elapsed before a signed find is attempted, the signed id will no longer be valid, and nil is returned.

It’s possible to further restrict the use of a signed id with a purpose. This helps when you have a general base model, like a User, which might have signed ids for several things, like password reset or email verification. The purpose that was set during generation must match the purpose set when finding. If there’s a mismatch, nil is again returned.


signed_id = User.first.signed_id expires_in: 15.minutes, purpose: :password_reset

User.find_signed signed_id # => nil, since the purpose does not match

travel 16.minutes
User.find_signed signed_id, purpose: :password_reset # => nil, since the signed id has expired

User.find_signed signed_id, purpose: :password_reset # => User.first
Source code GitHub
# File activerecord/lib/active_record/signed_id.rb, line 52
def find_signed(signed_id, purpose: nil)
  raise if primary_key.nil?

  if id = signed_id_verifier.verified(signed_id, purpose: combine_signed_id_purposes(purpose))
    find_by primary_key => id

Works like find_signed, but will raise an ActiveSupport::MessageVerifier::InvalidSignature exception if the signed_id has either expired, has a purpose mismatch, is for another record, or has been tampered with. It will also raise an ActiveRecord::RecordNotFound exception if the valid signed id can’t find a record.


User.find_signed! "bad data" # => ActiveSupport::MessageVerifier::InvalidSignature

signed_id = User.first.signed_id
User.find_signed! signed_id # => ActiveRecord::RecordNotFound
Source code GitHub
# File activerecord/lib/active_record/signed_id.rb, line 72
def find_signed!(signed_id, purpose: nil)
  if id = signed_id_verifier.verify(signed_id, purpose: combine_signed_id_purposes(purpose))

The verifier instance that all signed ids are generated and verified from. By default, it’ll be initialized with the class-level signed_id_verifier_secret, which within Rails comes from the Rails.application.key_generator. By default, it’s SHA256 for the digest and JSON for the serialization.

Source code GitHub
# File activerecord/lib/active_record/signed_id.rb, line 81
def signed_id_verifier
  @signed_id_verifier ||= begin
    secret = signed_id_verifier_secret
    secret = if secret.respond_to?(:call)

    if secret.nil?
      raise ArgumentError, "You must set ActiveRecord::Base.signed_id_verifier_secret to use signed ids"
    else secret, digest: "SHA256", serializer: JSON, url_safe: true

Allows you to pass in a custom verifier used for the signed ids. This also allows you to use different verifiers for different classes. This is also helpful if you need to rotate keys, as you can prepare your custom verifier for that in advance. See ActiveSupport::MessageVerifier for details.

Source code GitHub
# File activerecord/lib/active_record/signed_id.rb, line 97
def signed_id_verifier=(verifier)
  @signed_id_verifier = verifier

Definition files