Re: [Pharo-users] Proper way of handling multiple exception sections

Oct. 25, 2013

      On 25 oct. 2013, at 13:34, Norbert Hartl <norbert@hartl.name> wrote:
...
Iâm thinking about what would be the proper/least annoying way of having multiple exception sections. If I have a code block that can emit two different exceptions is the only way doing it
[ [ ... ]
 on: Exception1
 do: [ â¦ ] ]
   on: Exception2
   do: [ â¦ ]
You can handle multiple exceptions like that:

[ ... ] on: Exception1, Exception2 do: [ :err | ... ]

But there is only one handling block.
If you need to have two different handling blocks, I once though of a solution where you would write things like that:

[ ... ] exceptionHandler
	on: Exception1 do: [ ... ];
	on: Exception2 do: [ ... ];
	execute.

The #exceptionHandler message would answer an ExceptionHandler on the block that would be able to manage multiple handling blocks.
Something like that:

ExceptionHandler >> on: anExceptionClass do: aBlock 
	handlingBlock at: anExceptionClass put: aBlock

ExceptionHandler>> handlingBlockFor: anExceptionClass
	anExceptionClass ifNil: [ ^ nil ]. 
	^ handlingBlock 
		at: anExceptionClass 
		ifAbsent: [ self handlingBlockFor: anExceptionClass superclass ]

ExceptionHandler >>#execute
	block on: Error do: [ :error | 
		(self handlingBlockFor: error class) 
			ifNil: [ error pass ]
			ifNotNil: [ :handlingBlock | handlingBlock value ] ]
...
on:do: just calls a primitive that marks the context being an exception handler. What is called in the image when the stack is scanned to find an exception handler?
I think its ContextPart>>#findNextHandlerContextStarting
...
thanks,
Norbert

Re: [Pharo-users] Proper way of handling multiple exception sections

Camille Teruel