On Sun, Sep 11, 2011 at 4:00 PM, Chanan
Berler
<[email protected]>
wrote:
is this better ?
No. Eval is bad! :)
Imagine you send improper text that could be interpreted as
actual code. Imagine someone else being able to send stuff
to that service and sends something malicious. Imagine
someone not knowing what they're suppose to send, and they
just send commands.
Instead, I suggest one of two options:
1. Using some form of syntax to say "please look into this
key, and then that key, and then this index number for the
value" and then using some parser (or writing your own) that
is able to understand it. This is what's done in XPath, CSS
selector paths, etc.
2. sending the data itself instead of sending a reference to
where the data may be. I suggest JSON,
I've gone ahead and written the 1st option, for fun:
#!/usr/bin/perl
use strict;
use warnings;
{
package NewHash;
use Tie::Hash;
our @ISA = ('Tie::StdHash');
sub FETCH {
my ( $object, $path ) = @_;
my @paths = split /\//, $path;
return iterate( $object->{ shift @paths }, @paths
);
}
sub iterate {
my ( $object, @paths ) = @_;
my $next = shift @paths if @paths;
if ( ref $object eq 'HASH' ) {
return defined $next ? iterate(
$object->{$next}, @paths ) : $object;
} elsif ( ref $object eq 'ARRAY' ) {
return defined $next ? iterate(
$object->[$next], @paths ) : $object;
}
if ( $next && ! ref $object ) {
die 'Unsupported reference type: ' . ref
$object;
}
return $object;
}
}
my %hash;
tie %hash, 'NewHash';
%hash = (
key1 => {
key2 => [ 'val' ],
},
);
my $location = 'key1/key2/0';
print $hash{$location}; # prints 'val'
print $hash{'key1'}; # prints { key2 => ['val'] }
print $hash{'key1/key2'}; # prints ['val']
-----
This recurses over the path, and goes deeper for every
result until it either finds the exact location or reaches a
scalar, which should be the last location. It doesn't
support SCALAR refs or CODE refs or Regexp refs, but it can
be adapted to support them.
The problem here is what if the key name contains a forward
slash? Ah, the fallacy of simple parsing. :)
Good luck.
S.
