class Devise::Strategies::Rememberable

authenticatable.
recreate the user from this cookie if it exists. Must be called before
to verify whether there is a cookie with the remember token, and to
Remember the user through the remember token. This strategy is responsible

def authenticate!

strategy handle the authentication.
the record in the database. If the attempt fails, we pass to another
To authenticate a user we deserialize the cookie and attempt finding 
def authenticate!
  resource = mapping.to.serialize_from_cookie(*remember_cookie)
  if validate(resource)
    success!(resource)
  elsif !halted?
    cookies.delete(remember_key)
    pass
  end
end

def decorate(resource) 

def decorate(resource)
  super
  resource.extend_remember_period = mapping.to.extend_remember_period if resource.respond_to?(:extend_remember_period=)
end

def remember_cookie 

def remember_cookie
  @remember_cookie ||= cookies.signed[remember_key]
end

def remember_key 

def remember_key
  "remember_#{scope}_token"
end

def remember_me? 

def remember_me?
  true
end

def valid?

A valid strategy for rememberable needs a remember token in the cookies. 
def valid?
  @remember_cookie = nil
  remember_cookie.present?
end