On Thursday, Jun 5, 2003, at 13:07 US/Pacific, Andrew Brosnan wrote: [..]
my $hash = {};
while (my $rows = $response->fetchrow_hashref){ $hash->{$rows->{task_ID}} = $rows; }
Why is hash declared as my $hash and not my %hash? and how does the
This creates an annonymous hash '{}' and stores a reference to that hash
in $hash.
As for solving -
when to use a reference to a hash,
vice declaring a hash itself.Some of it is merely 'art work' - but there is a useful
practical distinction, is one planning to
pass by 'value' or pass by 'reference' at
any time in the life of the variable. { and/or
all of the future refactorings of the code.... 8-) }One can have a large hash, and if you pass it by value then you have to put all of the key/value pairs onto the stack. While if you passed merely a reference to the hash, you will pass merely the singular reference itself.
I just hacked something where I was not sure what the structure would really need to look like, so opted to merely declare
my $struct;
....
$struct->{$sname} = "src: $src_file open error:\n\t $!";
....
$struct->{$sname} = "copy of $src_file ok";
...so technically the code does not WARN the coder that I plan to use it as a reference to a hash.... but looking at the various places where I used it, most perl coders would understand that it was merely a hash.
I also do this sort of trick when I am planning to do strange return solutions:
sub some_funktion
{
....
return undef unless($condition_one);
....return "that's not right" if $error_case ;
$hash_ref;
}hence I can 'know' a bit about what went on with
my $got_back = some_funktion(@arglist);
unless(defined($got_back)) {
# condition_one not met
....
} unless(ref($got_back)) {
#
# that's not right handle the error_case
#
} while(my ($k,$v) = each %$got_back))
{
#
# here we deal with it just like it were a regular hash
#
}HTH....
ciao drieux
---
-- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
