token for temporary values

application_record.rb

has_many :tokens, as: :tokenable, dependent: :destroy

create_tokens.rb

class CreateTokens < ActiveRecord::Migration[5.0]
  def change
    create_table :tokens do |t|
      t.string :token, null: false
      t.references :tokenable, polymorphic: true, null: false

      t.timestamps
    end
  end
end

token.rb

class Token < ApplicationRecord
  belongs_to :tokenable, polymorphic: true

  validates :token, presence: true
  validates :tokenable, presence: true

  before_validation on: :create do
    self.token = SecureRandom.hex(12)
  end

  def self.claim(key, must = true)
    token = Token.find_by(token: key)
    if token
      object = token.tokenable
      token.destroy
      return object
    else
      if must
        raise ActiveRecord::RecordNotFound
      else
        return nil
      end
    end
  end

  def self.claim!(key)
    self.claim(key, true)
  end

  def self.for(object)
    Token.create!(tokenable: object)
  end

  def to_s
    token
  end

end