Hash::Fold - flatten and unflatten nested hashrefs
use Hash::Fold qw(flatten unflatten);
my $object = bless { foo => 'bar' };
my $nested = {
foo => $object,
baz => {
a => 'b',
c => [ 'd', { e => 'f' }, 42 ],
},
};
my $flattened = flatten($nested);
is_deeply $flattened, {
'baz.a' => 'b',
'baz.c.0' => 'd',
'baz.c.1.e' => 'f',
'baz.c.2' => 42,
'foo' => $object,
};
my $roundtrip = unflatten($flattened);
is_deeply $roundtrip, $nested;This module provides functional and OO interfaces which can be used to flatten, unflatten and merge nested hashrefs.
Unless noted, the functions listed below are also available as methods. Options provided to the Hash::Fold constructor can be supplied to the functions, e.g.:
use Hash::Fold;
my $folder = Hash::Fold->new(delimiter => '/');
$folder->fold($hash);is equivalent to:
use Hash::Fold qw(fold);
my $folded = fold($hash, delimiter => '/');Options (and constructor args) can be supplied as a list of key/value pairs or a hashref, so the following are equivalent:
my $folded = fold($hash, delimiter => '/' );
my $folded = fold($hash, { delimiter => '/' });In addition, Hash::Fold uses Sub::Exporter, which allows functions to be imported with options baked in, e.g.:
use Hash::Fold fold => { delimiter => '/' };
my $folded = fold($hash);As described above, the following options can be supplied as constructor args, import args, or per-function overrides. Under the hood, they are (Moo) attributes which can be wrapped and overridden like any other attributes.
Type: Str, ro, default: "."
The delimiter prefixed to array elements when flattening and unflattening.
Type: Str, ro, default: "."
The delimiter prefixed to hash elements when flattening and unflattening.
Type: Str
This is effectively a write-only attribute which assigns the same string to
array_delimiter and hash_delimiter.
It can only be supplied as a constructor arg or function option (which are
equivalent) i.e. Hash::Fold instances have no delimiter method.
Type: (Hash::Fold, Ref) → None, ro
A callback invoked whenever fold encounters a circular reference
i.e. a reference which contains itself as a nested value.
The callback is passed two arguments: the Hash::Fold instance and the value, e.g.:
sub on_cycle {
my ($folder, $value) = @_;
warn 'self-reference found: ', Dumper(value), $/;
}
my $folder = Hash::Fold->new(on_cycle => \&on_cycle);Note that circular references are handled correctly i.e. they are treated as terminals and not traversed. This callback merely provides a mechanism to report them (e.g. by issuing a warning).
The default callback does nothing.
Type: (Hash::Fold, Ref) → Any, ro
A callback invoked whenever fold encounters a value for which the
is_object method returns true i.e. any reference that isn't an
unblessed arrayref or unblessed hashref. This callback can be used to modify
the value, e.g. to return a traversable value (e.g. unblessed hashref) in place
of a terminal (e.g. blessed hashref).
The callback is passed two arguments: the Hash::Fold instance and the object, e.g.:
use Scalar::Util qw(blessed);
sub on_object {
my ($folder, $value) = @_;
if (blessed($value) && $value->isa('HASH')) {
return { %$value }; # unbless
} else {
return $value;
}
}
my $folder = Hash::Fold->new(on_object => \&on_object);The default callback returns its value unchanged.
Nothing by default. The following functions can be imported.
Signature: (HashRef [, Hash|HashRef ]) → HashRef
Takes a nested hashref and returns a single-level hashref with (by default)
dotted keys. The delimiter can be overridden via the delimiter,
array_delimiter and hash_delimiter
options.
Unblessed arrayrefs and unblessed hashrefs are traversed. All other values
(e.g. strings, regexps, objects etc.) are treated as terminals and passed
through verbatim, although this can be overridden by supplying a suitable
on_object callback.
Signature: (HashRef [, Hash|HashRef ]) → HashRef
Provided as an alias for fold.
Signature: (HashRef [, Hash|HashRef ]) → HashRef
Takes a flattened hashref and returns the corresponding nested hashref.
Signature: (HashRef [, Hash|HashRef ]) → HashRef
Provided as an alias for unfold.
Signature: (HashRef [, HashRef... ]) → HashRef
Signature: (ArrayRef<HashRef> [, Hash|HashRef ]) → HashRef
Takes a list of hashrefs which are then flattened, merged into one (in the order provided i.e. with precedence given to the rightmost arguments) and unflattened i.e. shorthand for:
unflatten { map { %{ flatten $_ } } @_ }To provide options to the merge subroutine, pass the hashrefs in an arrayref,
and the options (as usual) as a list of key/value pairs or a hashref:
merge([ $hash1, $hash2, ... ], delimiter => ... )
merge([ $hash1, $hash2, ... ], { delimiter => ... })Signature: Any → Bool
This method is called from fold to determine whether a value should
be passed to the on_object callback.
It is passed each value encountered while traversing a hashref and returns true for all references (e.g. regexps, globs, objects etc.) apart from unblessed arrayrefs and unblessed hashrefs, and false for all other values (i.e. unblessed hashrefs, unblessed arrayrefs, and non-references).
1.0.0
Copyright © 2014-2021 by chocolateboy.
This is free software; you can redistribute it and/or modify it under the terms of the Artistic License 2.0.