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Test2::Util::HashBase(3pm) User Contributed Perl Documentation Test2::Util::HashBase(3pm)


Test2::Util::HashBase - Build hash based classes.


A class:

    package My::Class;
    use strict;
    use warnings;

    # Generate 3 accessors
    use Test2::Util::HashBase qw/foo -bar ^baz/;

    # Chance to initialize defaults
    sub init {
        my $self = shift;    # No other args
        $self->{+FOO} ||= "foo";
        $self->{+BAR} ||= "bar";
        $self->{+BAZ} ||= "baz";

    sub print {
        print join ", " => map { $self->{$_} } FOO, BAR, BAZ;

Subclass it

    package My::Subclass;
    use strict;
    use warnings;

    # Note, you should subclass before loading HashBase.
    use base 'My::Class';
    use Test2::Util::HashBase qw/bat/;

    sub init {
        my $self = shift;

        # We get the constants from the base class for free.
        $self->{+FOO} ||= 'SubFoo';
        $self->{+BAT} ||= 'bat';


use it:

    package main;
    use strict;
    use warnings;
    use My::Class;

    my $one = My::Class->new(foo => 'MyFoo', bar => 'MyBar');

    # Accessors!
    my $foo = $one->foo;    # 'MyFoo'
    my $bar = $one->bar;    # 'MyBar'
    my $baz = $one->baz;    # Defaulted to: 'baz'

    # Setters!
    $one->set_foo('A Foo');

    #'-bar' means read-only, so the setter will throw an exception (but is defined).
    $one->set_bar('A bar');

    # '^baz' means deprecated setter, this will warn about the setter being
    # deprecated.
    $one->set_baz('A Baz');

    $one->{+FOO} = 'xxx';


This package is used to generate classes based on hashrefs. Using this class will give you a "new()" method, as well as generating accessors you request. Generated accessors will be getters, "set_ACCESSOR" setters will also be generated for you. You also get constants for each accessor (all caps) which return the key into the hash for that accessor. Single inheritance is also supported.


This is a bundled copy of Object::HashBase. This file was generated using the "/home/exodist/perl5/perlbrew/perls/main/bin/" script.



$it = $class->new(@VALUES)
Create a new instance using key/value pairs.

HashBase will not export "new()" if there is already a "new()" method in your packages inheritance chain.

If you do not want this method you can define your own you just have to declare it before loading Test2::Util::HashBase.

    package My::Package;

    # predeclare new() so that HashBase does not give us one.
    sub new;

    use Test2::Util::HashBase qw/foo bar baz/;

    # Now we define our own new method.
    sub new { ... }

This makes it so that HashBase sees that you have your own "new()" method. Alternatively you can define the method before loading HashBase instead of just declaring it, but that scatters your use statements.


This gives you the chance to set some default values to your fields. The only argument is $self with its indexes already set from the constructor.


To generate accessors you list them when using the module:

    use Test2::Util::HashBase qw/foo/;

This will generate the following subs in your namespace:

Getter, used to get the value of the "foo" field.
Setter, used to set the value of the "foo" field.
Constant, returns the field "foo"'s key into the class hashref. Subclasses will also get this function as a constant, not simply a method, that means it is copied into the subclass namespace.

The main reason for using these constants is to help avoid spelling mistakes and similar typos. It will not help you if you forget to prefix the '+' though.


You can subclass an existing HashBase class.

    use base 'Another::HashBase::Class';
    use Test2::Util::HashBase qw/foo bar baz/;

The base class is added to @ISA for you, and all constants from base classes are added to subclasses automatically.


The source code repository for HashBase can be found at


Chad Granum <>


Chad Granum <>


Copyright 2016 Chad Granum <>.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


2017-01-13 perl v5.24.1