Bjoern Hoehrmann <[EMAIL PROTECTED]> writes:
>* Tassilo von Parseval wrote:
>>On Mon, Aug 23, 2004 at 08:14:45AM +0200 Bjoern Hoehrmann wrote:
>>
>>> Should my XS code check whether an object 'can' a specific method
>>> before calling call_method() for a reason other than performance? It
>>> seems that such a check is not commonly performed so it is probably
>>> not very important.
>>
>>Depends. When writing pure Perl code, do you usually check that a method
>>exists before you call it? I'd say no. However, sometimes you may want
>>to do it. The same is true for XS. If it's crucial not to trigger a
>>non-existent method, then do a preliminary check.
>
>Right, I looked at it in the context of optional event handlers where
>it is common that specific methods do not exist. In Perl, if $o->x is
>called even though there is no method x, Perl would die; so my question
>is rather whether call_method for a non-existant method has negative
>side-effects.
Calling the method and catching the die via
call_method("Not_there",G_SCALARX|G_EVAL);
is what I do in Tk. But Tk has the G_EVAL there anyway so
that any die is reported in Tk context.
>
>>> What's the best way to check whether an object 'can' a specific
>>> method?
>>
>>You can use 'gv_fetchmethod_autoload':
>>
>> /* assuming 'obj' holds the object reference */
>> HV *stash = HvSTASH((SV*)SvRV(obj));
>>
>> if (!gv_fetchmethod_autoload(stash, "method", FALSE))
>> croak("'method' does not exist");
>> else
>> /* call it */
>>
>>If you want to allow 'method' to be autoloaded, set the third parameter
>>to TRUE.
>
>Thanks!
