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Re: Handling cascading defaults

by mikfire (Deacon)
on Aug 19, 2000 at 18:28 UTC ( #28636=note: print w/replies, xml ) Need Help??


in reply to Handling cascading defaults

I hope I have understood your question correctly. Your basic problem is that you want to have a default error handler that can be easily overridden, right?

If so, then the trick we use in my shop works kinda like this:

package Error; use var qw/$ERROR_HANDLER/; @ISA = qw/ EXPORTER /; @EXPORT_OK = qw/ &Error /; $ERROR_HANDLER = undef; # Because I need to be sure sub Error { if ( defined( $ERROR_HANDLER ) ) { $ERROR_HANDLER->($@); } else { print STDERR "@_\n"; } }
The default behaviour is to print a nice message to STDERR. If somebody sets $ERROR::ERROR_HANDLER to a subroutine reference, though, that function will be called instead. Yes, there are a few holes in the code I have presented, but the idea works ( fixing them has been left as an excercise to the reader :).

There isn't a lot of magic in CGI.pm. An object is simply a package, after all. To get the procedural methods made available, they simply put them in the @EXPORT. CGI.pm does use its own import method, but those are pretty easy to write as well. It is also pretty easy to write functions that can be used as either method calls or as procedural functions ( simply shift the first element off @_ and decide if it is an object reference of the correct type or not ).

mikfire

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