blog_rails_api_auth_pt_2_7.rb

# app/models/user.rb

class User < ActiveRecord::Base
  # ...

  def self.for_authentication(token)
    where(authentication_token: token).
      where('authentication_token_expires_at > ?', Time.current).
      first
  end
end

# app/strategies/token_authentication_strategy.rb

class TokenAuthenticationStrategy < Warden::Strategies::Base
  # ...

  def user
    @user ||= User.for_authentication(token)
  end
end