NAME

Data::Walk::Prune - A way to say what should be removed

SYNOPSIS

        #!perl
        use Modern::Perl;
        use Moose::Util qw( with_traits );
        use Data::Walk::Extracted 0.019;
        use Data::Walk::Prune 0.011;
        use Data::Walk::Print 0.015;

        my  $edward_scissorhands = with_traits(
                        'Data::Walk::Extracted',
                        ( 
                                'Data::Walk::Prune', 
                                'Data::Walk::Print',
                        ),
                )->new( change_array_size => 1, );#Default
        my  $firstref = {
                        Helping => [
                                'Somelevel',
                                {
                                        MyKey => {
                                                MiddleKey => {
                                                        LowerKey1 => 'low_value1',
                                                        LowerKey2 => {
                                                                BottomKey1 => 'bvalue1',
                                                                BottomKey2 => 'bvalue2',
                                                        },
                                                },
                                        },
                                },
                        ],
                };
        my      $result = $edward_scissorhands->prune_data(
                        tree_ref    => $firstref, 
                        slice_ref   => {
                                Helping => [
                                        undef,
                                        {
                                                MyKey => {
                                                        MiddleKey => {
                                                                LowerKey1 => {},
                                                        },
                                                },
                                        },
                                ],
                        },
                );
        $edward_scissorhands->print_data( $result );
    
        ######################################################################################
        #     Output of SYNOPSIS
        # 01 {
        # 02    Helping => [
        # 03            'Somelevel',
        # 04            {
        # 05                    MyKey => {
        # 06                            MiddleKey => {
        # 07                                    LowerKey2 => {
        # 08                                            BottomKey1 => 'bvalue1',
        # 09                                            BottomKey2 => 'bvalue2',
        # 10                                    },
        # 12                            },
        # 13                    },
        # 14            },
        # 15    ],
        # 16 },
        ######################################################################################

DESCRIPTION

This Moose::Role implements the method prune_data. It takes a tree_ref and a slice_ref and uses Data::Walk::Extracted. To remove portions of the 'tree_ref' defined by the 'slice_ref'. The cut points are defined by an empty hash_ref (no keys) or an empty array_ref (no positions). If the cut indicators are on a branch of the slice_ref that does not exist on the tree_ref then no cut takes place.

USE

This is a Moose::Role. One way to incorporate this role into Data::Walk::Extracted. is MooseX::ShortCut::BuildInstance. or read Moose::Util for more class building information.

Attributes

Data passed to ->new when creating an instance. For modification of these attributes see "Methods". The ->new function will either accept fat comma lists or a complete hash ref that has the possible attributes as the top keys. Additionally some attributes that have all the following methods; get_$attribute, set_$attribute, has_$attribute, and clear_$attribute, can be passed to prune_data and will be adjusted for just the run of that method call. These are called 'one shot' attributes.

prune_memory

Definition: When running a prune operation any branch called on the pruner that does not exist in the tree will not be used. This attribute turns on tracking of the actual cuts made and stores them for review after the method is complete. This is a way to know if the cut was actually implemented.
Default undefined
Range 1 = remember the cuts | 0 = don't remember

Attributes in Data::Walk::Extracted - also affect the output.

Methods

prune_data( %args )

Definition: This is a method used to remove targeted parts of a data reference.

Accepts: a hash ref with the keys 'slice_ref' and 'tree_ref' (both required). The slice ref can contain more than one 'slice' location in the data reference.

tree_ref This is the primary data ref that will be manipulated and returned changed.
slice_ref This is a data ref that will be used to prune the 'tree_ref'. In general the slice_ref should match the tree_ref for positions that should remain unchanged. Where the tree_ref should be trimmed insert either an empty array ref or an empty hash ref. If this position represents a value in a hash key => value pair then the hash key is deleted. If this position represents a value in an array then the position is deleted/cleared depending on the attribute 'change_array_size' in Data::Walk::Extracted. If the slice ref diverges from the tree ref then no action is taken past the divergence, even if there is a mandated slice. (no auto vivication occurs!)
[attribute name] - attribute names are accepted with temporary attribute settings. These settings are temporarily set for a single "prune_data" call and then the original attribute values are restored. For this to work the the attribute must meet the necessary criteria.

Example

        $pruned_tree_ref = $self->prune_data(
                tree_ref => $tree_data,
                slice_ref => $slice_data,
                prune_memory => 0,
        );

Returns: The $tree_ref with any changes

set_prune_memory( $Bool )

Definition: This will change the setting of the "prune_memory" attribute.
Accepts: 1 = remember | 0 = no memory
Returns: nothing

get_prune_memory

Definition: This will return the current setting of the "prune_memory" attribute.
Accepts: nothing
Returns: A $Bool value for the current state

has_prune_memory

Definition: This will indicate if the "prune_memory" attribute is set
Accepts: nothing
Returns: A $Bool value 1 = defined, 0 = not defined

clear_prune_memory

Definition: This will clear the "prune_memory" attribute value (Not the actual prune memory)
Accepts: nothing
Returns: A $Bool value 1 = defined, 0 = not defined

has_pruned_positions

Definition: This answers if any pruned positions were stored
Accepts: nothing
Returns: A $Bool value 1 = pruned cuts are stored, 0 = no stored cuts

get_pruned_positions

Definition: This returns an array ref of stored cuts
Accepts: nothing
Returns: an ArrayRef - although the cuts were defined in one data ref this will return one data ref per cut. Each ref will go to the root of the original data ref.

number_of_cuts

Definition: This returns the number of cuts actually made
Accepts: nothing
Returns: an integer

Caveat utilitor

Because this uses Data::Walk::Extracted the final $tree_ref is a deep cloned where the $slice_ref passed through.

Supported one shot attributes

prune_memory
explanation

GLOBAL VARIABLES

$ENV{Smart_Comments}: The module uses Smart::Comments if the '-ENV' option is set. The 'use' is encapsulated in an if block triggered by an environmental variable to comfort non-believers. Setting the variable $ENV{Smart_Comments} in a BEGIN block will load and turn on smart comment reporting. There are three levels of 'Smartness' available in this module '###', '####', and '#####'.