Programming Ruby

The Pragmatic Programmer's Guide

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class Exception
Parent: Object
Version: 1.6


exception backtrace exception message set_backtrace

Descendents of class Exception are used to communicate between raise methods and rescue statements in begin/end blocks. Exception objects carry information about the exception---its type (the exception's class name), an optional descriptive string, and optional traceback information.

class methods
exception Exception.exception( [ aString ] ) -> anException

Creates and returns a new exception object, optionally setting the message to aString.

instance methods
backtrace exc.backtrace -> anArray

Returns any backtrace associated with the exception. The backtrace is an array of strings, each containing either ``filename:lineNo: in `method''' or ``filename:lineNo.''

def a
  raise "boom"

def b   a() end

begin   b() rescue => detail   print detail.backtrace.join("\n") end
prog.rb:2:in `a'
prog.rb:6:in `b'

exception exc.exception( [ aString ] ) -> anException or exc

With no argument, returns the receiver. Otherwise, creates a new exception object of the same class as the receiver, but with a different message.

message exc.message -> aString

Returns the message associated with this exception.

set_backtrace exc.set_backtrace( anArray ) -> anArray

Sets the backtrace information associated with exc. The argument must be an array of String objects in the format described in Exception#backtrace .

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Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
Copyright © 2001 by Addison Wesley Longman, Inc. This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at

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