Class: ExceptionHandlerSet

• Inheritance
• Description
• Instance protocol
  • Compatibility-VW5.4
  • queries
  • save evaluation
  • setup
  • testing
• Examples

Inheritance:

   Object
   |
   +--Collection
      |
      +--Set
         |
         +--Dictionary
            |
            +--IdentityDictionary
               |
               +--ExceptionHandlerSet

Package:

stx:libbasic

Category:

Kernel-Exceptions

Version:

rev: 1.25 date: 2021/01/20 14:25:11

user: cg

file: ExceptionHandlerSet.st directory: libbasic

module: stx stc-classLibrary: libbasic

Description:

An ExceptionHandlerSet allows a group of unrelated signals to be handled
by individual handlers - their evaluation is equivalent to a corresponding
number of nested signal handlers, but more efficient and
somwehat easier to program and read.

copyright
COPYRIGHT (c) 1999 by eXept Software AG
             All Rights Reserved

This software is furnished under a license and may be used
only in accordance with the terms of that license and with the
inclusion of the above copyright notice.   This software may not
be provided or otherwise made available to, or used by, any
other person.  No title to or ownership of the software is
hereby transferred.

Instance protocol:

 on: aSignalOrException handle: aHandler

add a handler for aSignal to the set

 accepts: aSignalOrExceptionClass

return true, if the receiver accepts the argument, aSignal.
(i.e. if any of the receiver's elements is aSignal or a parent of it).

 exceptionHandlerFor: anException in: aContext

answer the exceptionHandler for anException from aContext.

 handlerForSignal: signal

answer the handler block for signal

 handlerForSignal: exceptionCreator context: theContext originator: originator

answer the handler block for the signal from originator.
The block is retrieved from aContext.
Answer nil if the signal is not handled

 handlerProtectedBlock: doBlock inContext: context

set the handlerProtectedBlock in context

 handles: anException

return true, if the receiver handles the argument, anException.
(i.e. if any of the receiver's elements handles anException).

Usage example(s):

(eachExceptionHandler handles:anException) ifTrue:[^ true]

 handleDo: aBlock

evaluate the argument, aBlock.
If any of the signals in the receiver is raised during evaluation,
evaluate the handleBlock passing it an Exception argument.
The handler may decide how to react to the signal by sending
a corresponding message to the exception (see there).
If the signal is not raised, return the value of evaluating
aBlock.

Usage example(s):

|h num| h := ExceptionHandlerSet new. h on:(Number divisionByZeroSignal) handle:[:ex | 'division by zero' printNL. ex proceed]. h on:(Object haltSignal) handle:[:ex | 'halt encountered ' printNL. ex proceed]. h on:(Float domainErrorSignal) handle:[:ex | 'domain error ' printNL. ex proceed]. h handleDo:[ num := 0. 'now dividing' printNL. 1 // num. 'now doing bad arcSin' printNL. num := 50. num arcSin. 'now halting' printNL. self halt. ]

 handleDo: aBlock from: originator

evaluate the argument, aBlock.
If any of the signals in the receiver is raised during evaluation,
evaluate the handleBlock passing it an Exception argument.
The handler may decide how to react to the signal by sending
a corresponding message to the exception (see there).
If the signal is not raised, return the value of evaluating
aBlock.

Usage example(s):

|h num| h := ExceptionHandlerSet new. h on:(Number divisionByZeroSignal) handle:[:ex | 'division by zero' printNL. ex proceed]. h on:(Object haltSignal) handle:[:ex | 'halt encountered ' printNL. ex proceed]. h on:(Float domainErrorSignal) handle:[:ex | 'domain error ' printNL. ex proceed]. h handleDo:[ 'now halting' printNL. self halt. 'the following exceptions are not handled. A debugger is opened' printNL. 'now dividing' printNL. num := 0. 1 // num. 'now doing bad arcSin' printNL. num := 50. num arcSin. ] from:self

 on: anExceptionHandlerOrHandlerCollection do: aHandlerBlock

add a handler for aSignal to the set.
anExceptionHandlerOrHandlerCollection may be a single exceptionHandler or
a Collection of exceptionHandlers (e.g. Array or SignalSet)

 isExceptionHandler

return true, if the receiver responds to the exception handler protocol,
especially to the #accepts: and #handles: messages

Examples:

         |h num|

         h := ExceptionHandlerSet new.
         h on:ZeroDivide
           do:[:ex | 'division by zero' printCR. ex proceed].

         h on:HaltInterrupt
           do:[:ex | 'halt encountered ' printCR. ex proceed].

         h on:DomainError
           do:[:ex | 'domain error  ' printCR. ex proceed].

         h handleDo:[
            num := 0.

            'now dividing' printCR.
            1 // num.

            'now doing bad arcSin' printCR.
            num := 50.
            num arcSin.

            'now halting' printCR.
            self halt.
         ]

         |h num|

         h := ExceptionHandlerSet new.
         h on:ZeroDivide
           do:[:ex | 'division by zero' printCR. ex proceed].

         h on:HaltInterrupt
           do:[:ex | 'halt encountered ' printCR. ex proceed].

         h on:DomainError
           do:[:ex | 'domain error ' printCR. ex proceed].

         [
            num := 0.

            'now dividing' printCR.
            1 // num.

            'now doing bad arcSin' printCR.
            num := 50.
            num arcSin.

            'now halting' printCR.
            self halt.
         ] valueWithExceptionHandler:h