Rightyright. I have a hash reference which contains an unknown amount of hash references as values, which themselves contain hash references...and so on ad finitum, you know the drill. We'll call it $structure. That's all very easy to access when I know what I'm looking for. But, say I get a series of keys from a user, and have them in an array. The array looks like this:

('stuff', 'hierarchy', 'album')

Here, stuff is the first-level key of the structure, hierarchy is the hash reference returned by $structure->{stuff}, et cetera, et cetera. To write it in Perl, this chain would look like this:

$structure->{stuff}{hierarchy}{album}

I figured out a way to descend the structure when I only have to locate a value from it based on that list:

my $target = 'bar';    # the end key

my $path = ('stuff', 'hierarchy', 'album');

my $nodule = $structure;

while (my $next_key = shift @path) {
    $nodule = $nodule->{$next_key};
}

my $triumphant = $nodule->{$target};

[download]

That made me feel pretty good. But then the jig was up: I had to change a value in the structure. Essentially, I had to change $nodule->{$target}. I can't just convert that - it needs to be reflected as a change in the whole $structure, and I'm wiping out the rest of the structure as I go along. The only way I can think of doing this at the moment is by constructing an elaborate eval STRING statement by concatenating the list into Perl syntax and running that. But that introduces a whole range of new concerns, and I don't really want to do that. There must be another way.



--
my one true love

In reply to descending a tree of hash references by Amoe

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