Ruby custom error classes: inheritance of the message attribute

I can't seem to find much information about custom exception classes.

What I do know

You can declare your custom error class and let it inherit from StandardError, so it can be rescued:

class MyCustomError < StandardErrorend

This allows you to raise it using:

raise MyCustomError, "A message"

and later, get that message when rescuing

rescue MyCustomError => e  puts e.message # => "A message"

What I don't know

I want to give my exception some custom fields, but I want to inherit the message attribute from the parent class. I found out reading on this topic that @message is not an instance variable of the exception class, so I'm worried that my inheritance won't work.

Can anyone give me more details to this? How would I implement a custom error class with an object attribute? Is the following correct:

class MyCustomError < StandardError  attr_reader :object  def initialize(message, object)    super(message)    @object = object  endend

And then:

raise MyCustomError.new(anObject), "A message"

to get:

rescue MyCustomError => e  puts e.message # => "A message"  puts e.object # => anObject

will it work, and if it does, is this the correct way of doing things?