module SystemError

Overview

This module can be included in any Exception subclass that is used to wrap some system error (Errno or WinError).

It adds an #os_error property that contains the original system error. It provides several constructor methods that set the #os_error value:

• .from_os_error receives an OS error value and creates an instance with that.
• .from_errno constructs an instance with the current LibC errno value (Errno.value).
• .from_winerror constructs an instance with the current LibC winerror value (WinError.value).

An error message is automatically constructed based on the system error message.

For example:

class MyError < Exception
  include SystemError
end

MyError.from_errno("Something happened")

Customization

Including classes my override several protected methods to customize the instance creation based on OS errors:

• protected def build_message(message, **opts) Prepares the message that goes before the system error description. By default it returns the original message unchanged. But that could be customized based on the keyword arguments passed to from_errno or from_winerror.
• protected def new_from_os_error(message : String?, os_error, **opts) Creates an instance of the exception that wraps a system error. This is a factory method and by default it creates an instance of the current class. It can be overridden to generate different classes based on the #os_error value or keyword arguments.
• protected def os_error_message(os_error : Errno | WinError | Nil, **opts) : String? Returns the respective error message for os_error. By default it returns the result of Errno#message or WinError#message. This method can be overridden for customization of the error message based on or_error and opts.

Direct including types

• IO::Error
• RuntimeError

Defined in:

system_error.cr

Instance Method Summary

• #os_error : Errno | WinError | Nil

  The original system error wrapped by this exception

Instance Method Detail