Foreach and referencing complex hashes

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February 27th, 2013, 10:04 AM

gw1500se

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Foreach and referencing complex hashes

I can never seem to get my head around hash references and need some help. I have an XML hash and I need to process a set of sub-hashes (is that a valid term?). Here is my current non-working loop:

Code:

foreach my $id (%{$xml->{children}->{content}}) {
        print($id->{title}."\n");
}

The reference $xml->{children}->{content} is a series of hash keys (ids). Among the elements of each is 'title' ($xml->{children}->{content}->{<some id>}->{title}) and that is what I want to extract. However, I cannot come up with the syntax that gets the hash rather than the key. Can someone give me the correct syntax to do what I want? TIA.

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February 27th, 2013, 10:47 AM

gw1500se

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Never mind. I got it, sheesh!

Code:

foreach my $id (keys %{$xml->{children}->{content}}) {
        print($xml->{children}->{content}->{$id}->{title}."\n");
}

February 27th, 2013, 12:41 PM

keath

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I expect that you can drop most of the arrows.

Code:

foreach my $id (keys %{$xml->{children}{content}}) {
        print($xml->{children}{content}{$id}{title}."\n");
}

When you have a reference, only the first arrow is necessary.

Also, this might not be helpful, but when you are reaching into such deeply nested structures, and the thing you want to work with isn't the key, you can pull out just the hash or element you want to work with.

Example:

Code:

foreach my $content (values %{$xml->{children}{content}}) {
        print($content->{title}."\n");
}

By asking for the value, you can put that into a variable and have a direct reference to the hash you need to work with without having to reference the entire structure each time.

Comments on this post

gw1500se agrees: Thanks.

February 27th, 2013, 12:54 PM

gw1500se

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Ah ha! Values was what I was really looking for to eliminate all that repeated nesting. Thanks.

Foreach and referencing complex hashes

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