[Seaside-dev] exception handler instance creation

[Julian Fitzell]

The quick test for this one is to create a subclass of Object,
implement #handles: on the class side to return true, and then try
using it in an #on:do: block:

[Error signal] on: TheSubclass do: [:e | Transcript show: 'it works']

You may also have to implement #, to return an ExceptionSet but if
things basically work then this code will be fine. If not, the
question becomes, how hard is it to make it work. I'm downloading
GLASS at the moment and will give it a try once I have it installed
unless you get to it first.

Julian

On Tue, Jan 6, 2009 at 5:23 PM, James Foster <Smalltalk at jgfoster.net> wrote:
> As a general matter, my goal is to make GemStone accept anything that is
> ANSI compliant. I'll investigate further and get back to the group when I've
> got Seaside 2.9 loaded into GemStone (which is my current project).
>
> James
>
> On Jan 1, 2009, at 11:31 AM, Julian Fitzell wrote:
>
>> On Thu, Jan 1, 2009 at 6:42 PM, Dale Henrichs
>> <dale.henrichs at gemstone.com> wrote:
>>>
>>> Julian,
>>>
>>> For the exception handling to work correctly in GemStone, we also need to
>>> have subclasses of Exception (ExceptionA in 2.x and in 3.x Exception).
>>> There's a fair amount of support code in Exception that is inherited and is
>>> needed for exceptions to work correctly.
>>>
>>> James Foster is very intimate with the 2.x exception handling mechanism
>>> and has been working with Seaside2.9 recently, so he can give a definitive
>>> answer.
>>
>> Well, we need to make the distinction between exceptions themselves
>> and what the ANSI spec calls "exception selectors". It seems that in
>> most (if not all) systems, the Exception class is also an "exception
>> selector" (as is ExceptionSet). What we're doing here isn't having
>> another class behave like an exception (which I would expect to have a
>> lot of support code) but like an "exception selector" (that is,
>> something which can be asked whether a particular exception should be
>> handled).
>>
>> But I'll wait for James to comment unless I get around to downloading
>> GLASS again myself in the meantime.
>>
>> Thanks,
>>
>> Julian
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