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Term::Table::HashBase

Section: User Contributed Perl Documentation (3)
Updated: 2024-03-08
Index

NAME

Term::Table::HashBase - Build hash based classes.

SYNOPSIS

A class:

    package My::Class;    use strict;    use warnings;    # Generate 3 accessors    use Term::Table::HashBase qw/foo -bar ^baz <bat >ban +boo/;    # Chance to initialize defaults    sub init {        my $self = shift;    # No other args        $self->{+FOO} ||= "foo";        $self->{+BAR} ||= "bar";        $self->{+BAZ} ||= "baz";        $self->{+BAT} ||= "bat";        $self->{+BAN} ||= "ban";        $self->{+BOO} ||= "boo";    }    sub print {        print join ", " => map { $self->{$_} } FOO, BAR, BAZ, BAT, BAN, BOO;    }

Subclass it

    package My::Subclass;    use strict;    use warnings;    # Note, you should subclass before loading HashBase.    use base 'My::Class';    use Term::Table::HashBase qw/bub/;    sub init {        my $self = shift;        # We get the constants from the base class for free.        $self->{+FOO} ||= 'SubFoo';        $self->{+BUB} ||= 'bub';        $self->SUPER::init();    }

use it:

    package main;    use strict;    use warnings;    use My::Class;    # These are all functionally identical    my $one   = My::Class->new(foo => 'MyFoo', bar => 'MyBar');    my $two   = My::Class->new({foo => 'MyFoo', bar => 'MyBar'});    my $three = My::Class->new(['MyFoo', 'MyBar']);    # Readers!    my $foo = $one->foo;    # 'MyFoo'    my $bar = $one->bar;    # 'MyBar'    my $baz = $one->baz;    # Defaulted to: 'baz'    my $bat = $one->bat;    # Defaulted to: 'bat'    # '>ban' means setter only, no reader    # '+boo' means no setter or reader, just the BOO constant    # 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');    # '<bat' means no setter defined at all    # '+boo' means no setter or reader, just the BOO constant    $one->{+FOO} = 'xxx';

DESCRIPTION

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

THIS IS A BUNDLED COPY OF HASHBASE

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

METHODS

PROVIDED BY HASH BASE

$it = $class->new(%PAIRS)

$it = $class->new(\%PAIRS)

$it = $class->new(\@ORDERED_VALUES)

Create a new instance.

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

If you do not want this method you can define your own you just have todeclare it before loading Term::Table::HashBase.

    package My::Package;    # predeclare new() so that HashBase does not give us one.    sub new;    use Term::Table::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 justdeclaring it, but that scatters your use statements.

The most common way to create an object is to pass in key/value pairs whereeach key is an attribute and each value is what you want assigned to thatattribute. No checking is done to verify the attributes or values are valid,you may do that in init() if desired.

If you would like, you can pass in a hashref instead of pairs. When you do sothe hashref will be copied, and the copy will be returned blessed as an object.There is no way to ask HashBase to bless a specific hashref.

In some cases an object may only have 1 or 2 attributes, in which case ahashref may be too verbose for your liking. In these cases you can pass in anarrayref with only values. The values will be assigned to attributes in theorder the attributes were listed. When there is inheritance involved theattributes from parent classes will come before subclasses.

HOOKS

$self->init(): This gives you the chance to set some default values to your fields. The onlyargument is $self with its indexes already set from the constructor.
Note: Term::Table::HashBase checks for an init using "$class->can('init')"during construction. It DOES NOT call can() on the created object. Also notethat the result of the check is cached, it is only ever checked once, the firsttime an instance of your class is created. This means that adding an init()method AFTER the first construction will result in it being ignored.

ACCESSORS

READ/WRITE

To generate accessors you list them when using the module:

    use Term::Table::HashBase qw/foo/;

This will generate the following subs in your namespace:

foo(): Getter, used to get the value of the "foo" field.
set_foo(): Setter, used to set the value of the "foo" field.
FOO(): Constant, returns the field "foo"'s key into the class hashref. Subclasses willalso get this function as a constant, not simply a method, that means it iscopied into the subclass namespace.
The main reason for using these constants is to help avoid spelling mistakesand similar typos. It will not help you if you forget to prefix the '+' though.

READ ONLY

    use Term::Table::HashBase qw/-foo/;

set_foo(): Throws an exception telling you the attribute is read-only. This is exported tooverride any active setters for the attribute in a parent class.

DEPRECATED SETTER

    use Term::Table::HashBase qw/^foo/;

set_foo(): This will set the value, but it will also warn you that the method isdeprecated.

NO SETTER

    use Term::Table::HashBase qw/<foo/;

Only gives you a reader, no "set_foo" method is defined at all.

NO READER

    use Term::Table::HashBase qw/>foo/;

Only gives you a write ("set_foo"), no "foo" method is defined at all.

CONSTANT ONLY

    use Term::Table::HashBase qw/+foo/;

This does not create any methods for you, it just adds the "FOO" constant.

SUBCLASSING

You can subclass an existing HashBase class.

    use base 'Another::HashBase::Class';    use Term::Table::HashBase qw/foo bar baz/;

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

GETTING A LIST OF ATTRIBUTES FOR A CLASS

Term::Table::HashBase provides a function for retrieving a list of attributes for anTerm::Table::HashBase class.

@list = Term::Table::HashBase::attr_list($class)
@list = $class->Term::Table::HashBase::attr_list(): Either form above will work. This will return a list of attributes defined onthe object. This list is returned in the attribute definition order, parentclass attributes are listed before subclass attributes. Duplicate attributeswill be removed before the list is returned.
Note: This list is used in the "$class->new(\@ARRAY)" constructor todetermine the attribute to which each value will be paired.