How can I walk a YAML tree with Perl's YAML::Tiny?

perl, yaml

Solution

Try

print "$_\n" for keys %{ $configuration->[0] };

You have to force the array element "`$configuration->[0]`" into a hash ref with "`%{...}`"

So to iterate over them:

for my $key ( keys %{ $configuration->[0] } ){
  my $value = $configuration->[0]{$key};

  print "$key => $value\n";
}

Problem

I have a YAML document like this: ``` --- version: 1 rootdirectory: - subdirectory: - file1 - file2 - subdirectory2 ``` that I am loading into a YAML::Tiny object like this: ``` $configuration = YAML::Tiny->read($configuration_file) ``` I see from invoking the script with the Perl debugger that what I end up with is a set of nested hashes and arrays that reflect the structure of the YAML source: ``` 0 YAML::Tiny=ARRAY(0x84e3ba4) 0 HASH(0x80627dc) 'rootdirectory' => ARRAY(0x84e3d3c) 0 HASH(0x84352b0) 'subdirectory' => ARRAY(0x84e3df0) 0 'file1' 1 'file2' 1 'subdirectory2' 'version' => 1 ``` So, I can do things like the following without problem: ``` print $configuration->[0]->{version} ``` and receive the expected answer of '1'. Likewise, I can also do: ``` print $configuration->[0]->{rootdirectory}->[0]->{subdirectory}->[0] ``` and receive the expected answer of 'file1'. My problem comes from all of the a priori knowledge I need to derive my filename in the above example. As I am trying to allow the users of my script to describe an arbitrary directory structure in the YAML configuration this isn't good enough. I need to be able to "walk" the tree from 'rootdirectory'. So, I would have imagined I could have done something like this: ``` print keys($configuration->[0]) ``` which I would have expected to have returned 'rootdirectory,version' ... and so on, iterating over the arrays and hashes until I had walked the tree. When I attempt to run the above example, I get: ``` Type of arg 1 to keys must be hash (not array element) ``` At this point I am stuck. As I understand it, $configuration->[0], whilst being an element of an array, is an element containing a hash that I believe I should be able to invoke the keys function against. What am I missing here?

Original source