NAME

Data::Focus::Lens::Dynamic - a lens that dynamically creates an appropriate lens for the target

SYNOPSIS

package Blessed::Data;

sub new {
    my ($class) = @_;
    return bless {
        secret_data => "hoge",
        accessible_by_lens => {
            a => "a for Blessed::Data"
        },
    }, $class;
}

sub Lens {
    my ($self, $param) = @_;
    require Data::Focus::Lens::HashArray::Index;
    return (
        Data::Focus::Lens::HashArray::Index->new(index => "accessible_by_lens", allow_blessed => 1)
        . Data::Focus::Lens::HashArray::Index->new(index => $param)
    );
}


package main;
use Data::Focus qw(focus);
use Data::Focus::Lens::Dynamic;

my $plain_data = { a => "a for plain_data" };
my $blessed_data = Blessed::Data->new;

my $lens = Data::Focus::Lens::Dynamic->new("a");
focus($plain_data)->get($lens);        ## => "a for plain_data";
focus($blessed_data)->get($lens);      ## => "a for Blessed::Data";

$plain_data->{a} = $blessed_data;
focus($plain_data)->get($lens, $lens); ## => "a for Blessed::Data";

DESCRIPTION

This is an implementation of Data::Focus::Lens, which dynamically creates an appropriate lens for the given target. The actual focusing job is delegated to the dynamically created lens.

CLASS METHOD

$lens = Data::Focus::Lens::Dynamic->new($param)

The constructor.

The $lens keeps the given $param. The $param is then passed to the dynamically created lens.

DELEGATION RULES

Here's how Data::Focus::Lens::Dynamic creates the lens object appropriate for the $target.

• If the $target is a blessed object and has Lens() method, it calls the Lens() method to obtain the appropriate lens.

  $appropriate_lens = $target->Lens($param)

  If Lens() method doesn't return a Data::Focus::Lens object, it throws an exception.

• If the $target is a non-blessed hash-ref or array-ref or undef, it creates a Data::Focus::Lens::HashArray::Index.

  $appropriate_lens = Data::Focus::Lens::HashArray::Index->new(index => $param)

• Otherwise, it does nothing. It creates no focal points.

OBJECT METHODS

apply_lens

See Data::Focus::Lens.

AUTHOR

Toshio Ito <debug.ito at gmail.com>