Re^2: using TIEHASH as wrapper/proxy, while avoiding recursion and warnings

The wrapper in Tie::Subset::Hash is a new variable.

I wanted to be able to tie the original variable while changing the original data.

This creates a lot of headaches to even access that data, to avoid recursion and related warnings.

> It's unclear to me what your proxy class is actually supposed to be doing?

Consider debugging, setting watchpoints, tracing, meta programming,...

It's not always possible to replace the monitored variable with a proxy, you just want to attach the magic directly.

There is code in the OP.

Cheers Rolf
_{(addicted to the Perl Programming Language :)

see Wikisyntax for the Monastery}

Comment on Re^2: using TIEHASH as wrapper/proxy, while avoiding recursion and warnings

Replies are listed 'Best First'.
Re^3: using TIEHASH as wrapper/proxy, while avoiding recursion and warnings by haukex (Archbishop) on Apr 22, 2024 at 13:29 UTC
I wanted to be able to tie the original variable while changing the original data. I see. I remember that when I tried something similar to that with tied filehandles, I got Perl to segfault, so I'm not sure if tie is meant to be used that way. It's not always possible to replace the monitored variable with a proxy, you just want to attach the magic directly. That's probably true, but I imagine it wouldn't be too difficult to refactor the code in question from using a hash to a hashref? Otherwise, if this is just for debugging, you could use refaliasing to replace the target hash with the tied hash? (though to unite you'd probably have to keep a reference to the original hash around) `use warnings; use strict; use feature 'refaliasing'; use Data::Dump; use Tie::Subset::Hash; my %hash; @hash{"a".."e"} = 41..45; dd \%hash; tie my %hash2, 'Tie::Subset::Hash', \%hash, ['b']; \%hash = \%hash2; dd \%hash; __END__ Aliasing via reference is experimental at foo.pl line 13. { a => 41, b => 42, c => 43, d => 44, e => 45 } { # tied Tie::Subset::Hash b => 42, }` [download]	[reply] [d/l]

Replies are listed 'Best First'.

Re^3: using TIEHASH as wrapper/proxy, while avoiding recursion and warnings
by haukex (Archbishop) on Apr 22, 2024 at 13:29 UTC

I wanted to be able to tie the original variable while changing the original data.

I see. I remember that when I tried something similar to that with tied filehandles, I got Perl to segfault, so I'm not sure if tie is meant to be used that way.

It's not always possible to replace the monitored variable with a proxy, you just want to attach the magic directly.

That's probably true, but I imagine it wouldn't be too difficult to refactor the code in question from using a hash to a hashref?

Otherwise, if this is just for debugging, you could use refaliasing to replace the target hash with the tied hash? (though to unite you'd probably have to keep a reference to the original hash around)

use warnings;
use strict;
use feature 'refaliasing';
use Data::Dump;
use Tie::Subset::Hash;

my %hash;
@hash{"a".."e"} = 41..45;

dd \%hash;

tie my %hash2, 'Tie::Subset::Hash', \%hash, ['b'];
\%hash = \%hash2;

dd \%hash;

__END__

Aliasing via reference is experimental at foo.pl line 13.
{ a => 41, b => 42, c => 43, d => 44, e => 45 }
{
  # tied Tie::Subset::Hash
  b => 42,
}
[download]

[reply]
[d/l]