NAME
Data::CSel::WrapStruct - Wrap data structure into a tree of objects suitable for use with Data::CSel
VERSION
This document describes version 0.008 of Data::CSel::WrapStruct (from Perl distribution Data-CSel-WrapStruct), released on 2020-04-15.
SYNOPSIS
use Data::CSel qw(csel);
use Data::CSel::WrapStruct qw(wrap_struct unwrap_tree);
my $data = [
0,
1,
[2, ["two","dua"], {url=>"http://example.com/two.jpg"}, ["even","prime"]],
3,
[4, ["four","empat"], {}, ["even"]],
];
my $tree = wrap_struct($data);
my @nodes = csel(":root > * > *:nth-child(4) > *", $tree);
my @tags = map { $_->value } @nodes; # -> ("even", "prime", "even")Scalars are wrapped using Data::CSel::WrapStruct::Scalar class, scalarrefs are wrapped using Data::CSel::WrapStruct::ScalarRef class, arrays are wrapped using Data::CSel::WrapStruct::Array class, and hashes are wrapped using Data::CSel::WrapStruct::Hash class. For convenience, when you load Data::CSel::WrapStruct, it adds Data::CSel::WrapStruct to @Data::CSel::CLASS_PREFIXES so you don't have to specify {class_prefixes=>["Data::CSel::WrapStruct"]} csel() option everytime.
my @hashes = map {$_->value} csel("Hash", $tree);
# -> ({url=>"http://example.com/two.jpg"}, {})The wrapper objects provide some methods, e.g.:
my @empty_hashes = map {$_->value} csel("Hash[length=0]", $tree);
# -> ({})
my @hashes_that_have_url_key = map {$_->value} csel("Hash[has_key('url')]", $tree);
# -> ({url=>"http://example.com/two.jpg"})
my @larger_scalars = [map {$_->value} csel("Scalar[value >= 3]", $tree)]
# -> (3, 4)See "NODE METHODS", "SCALAR NODE METHODS", "SCALARREF NODE METHODS", "ARRAY NODE METHODS", "HASH NODE METHODS" for more details on the provided methods.
You can replace the value of nodes using "value":
my @posint_scalar_nodes = csel("Scalar[value > 0]", $tree);
for (@posint_scalar_nodes) { $_->value( $_->value * 10 ) }
use Data::Dump;
dd unwrap_tree($data);
# => [
# 0,
# 10,
# [20, ["two","dua"], {url=>"http://example.com/two.jpg"}, ["even","prime"]],
# 30,
# [40, ["four","empat"], {}, ["even"]],
# ];DESCRIPTION
This module provides wrap_struct() which creates a tree of objects from a generic data structure. You can then perform node selection using Data::CSel's csel().
You can retrieve the original value of data items by calling value() method on the tree nodes.
NODE METHODS
parent
children
value
Usage:
my $val = $node->value; # get node value
$node->value(1); # set node valueGet or set node value.
Note that when setting node value, the new node value is not automatically wrapped for you. If you want to set new node value and expect to select it or part of it again with csel(), you will have to wrap the new value first with "wrap_struct".
remove
Usage:
$node->remove;Remove node from parent.
SCALAR NODE METHODS
In addition to methods listed in "NODE METHODS", Scalar nodes also have the following methods.
SCALARREF NODE METHODS
In addition to methods listed in "NODE METHODS", ScalarRef nodes also have the following methods.
ARRAY NODE METHODS
In addition to methods listed in "NODE METHODS", Array nodes also have the following methods.
length
Get array length. Can be used to select an array based on its length, e.g.:
@nodes = csel('Array[length > 0]');HASH NODE METHODS
In addition to methods listed in "NODE METHODS", Hash nodes also have the following methods.
length
Get the number of keys. Can be used to select a hash based on its number of keys, e.g.:
@nodes = csel('Hash[length > 0]');has_key
Usage:
my $bool = $node->has_key("foo");Check whether hash has a certain key. Can be used to select a hash, e.g.:
@nodes = csel('Hash[has_key("foo")]');key
Usage:
my $key_val = $node->key("foo");Get a hash key's value. Can be used to select a hash based on the value of one of its keys, e.g.:
@nodes = csel('Hash[key("name") = "lisa"]');FUNCTIONS
None exported by default, but exportable.
wrap_struct
Usage:
my $tree = wrap_struct($data);Wrap a data structure into a tree of objects.
Currently cannot handle recursive structure.
unwrap_tree
Usage:
my $data = unwrap_tree($wrapped_data);Unwrap a tree produced by "wrap_tree" back into unwrapped data structure.
FAQ
Changing the node value doesn't work!
my $data = [0, 1, 2];
my @nodes = csel("Scalar[value > 0]", wrap_struct($data));
for (@nodes) { $_->[0] = "x" }
use Data::Dump;
dd $data;still prints [0,1,2] instead of [0,'x','x']. Why?
To set node value, you have to use the value() node method with an argument:
...
for (@nodes) { $->value("x") }
...will then print the expected [0,'x','x'].
This module is slow!
If you intend to select a data structure with thousands of nodes or more, you're probably better off using other approach, for example Data::Walk::More. Data::Walk::More provides containers for the nodes you're traversing. For example, the CSel expression Hash[has_keys("foo")] > Array > Scalar[value > 0] can be written as:
walk sub {
my $ref = ref $_;
return if ref $_; # ... Scalar
return if $_ <= 0; # ... [value > 0]
return unless ref $Data::Walk::More::containers[-1] eq 'ARRAY'; # ... Array
return unless ref $Data::Walk::More::containers[-2] eq 'HASH'; # ... Hash
return unless exists $Data::Walk::More::containers[-2]{foo}; # ... [has_keys("foo")]
push @matches, $_;
}, $data;HOMEPAGE
Please visit the project's homepage at https://metacpan.org/release/Data-CSel-WrapStruct.
SOURCE
Source repository is at https://github.com/perlancar/perl-Data-CSel-WrapStruct.
BUGS
Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Data-CSel-WrapStruct
When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.
SEE ALSO
AUTHOR
perlancar <perlancar@cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2020, 2016 by perlancar@cpan.org.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.