Re: eval{}
- From: daggerquill@xxxxxxxxx (Jay Savage)
- Date: Mon, 6 Mar 2006 15:12:18 -0500
On 3/6/06, Tom Allison <tallison@xxxxxxxxxxx> wrote:
I ran into a potential problem when writing some code this weekend.
I'm running a network socket to pick up data and then run it against a
database connection before I return the response. Essentially it falls
into a few steps:
read from network
read from database
write to database
do something else on network
write to network
Being the cautious code writer I thought it would make sense to use
something like:
eval{
alarm(10);
"read from network"
"read from database"
....
}
But each of these database calls has it's own eval{} around the database
query (as an example):
my $rv;
eval {
$rv = $dbh->do($sql) or die $!;
};
if ( $@) {
die "FATAL!\n$@\n"
} else {
return $rv;
}
Which essentially means if I flattened out all the subroutines I would
end up with something like
eval {
...
eval {....}
if ($@) { }
eval { ... }
if ($@) {...}
}
if ($@) {
.....}
The problem I run into is throwing the exceptions up to the top eval{}
structure when I need to communicate that something didn't work right
so I can provide feedback to the network client connection.
I suppose I could try and rewrite the code to un-nest the eval{}
statements but I think that is avoiding learning something I should know
about how to manage eval{} for block exception handling.
Is there some way to rethrow or propogate errors or some tips on how to
manage this better?
die on errors and just keep passing them up the line:
eval {
eval {
eval {
bad_system_call() or die "$!\n";
} or die $@;
} or die $@;
};
print "eval says: $@\n" if $@;
As long as you keep propagating $@ in your die calls, the original
error message will get passed out.
HTH,
-- jay
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