Perl Cookbook

Using Classes as Structs

Problem

You’re used to structured data types more complex than Perl’s arrays and hashes, such as C’s structs and Pascal’s records. You’ve heard that Perl’s classes are comparable, but you aren’t an object-oriented programmer.

Solution

Use the standard Class::Struct module to declare C-like structures:

use Class::Struct;          # load struct-building module

struct Person => {          # create a definition for a "Person"
    name   => '$',          #    name field is a scalar
    age    => '$',          #    age field is also a scalar
    peers  => '@',          #    but peers field is an array (reference)
};

my $p = Person->new();      # allocate an empty Person struct

$p->name("Jason Smythe");                   # set its name field
$p->age(13);                                # set its age field
$p->peers( ["Wilbur", "Ralph", "Fred" ] );  # set its peers field

# or this way:
@{$p->peers} = ("Wilbur", "Ralph", "Fred");

# fetch various values, including the zeroth friend
printf "At age %d, %s's first friend is %s.\n",
    $p->age, $p->name, $p->peers(0);

Discussion

The Class::Struct::struct function builds struct-like classes on the fly. It creates a class of the name given in the first argument, and gives the class a constructor named new and per-field accessor methods.

In the structure layout definition, the keys are the names of the fields and the values are the data type. This type can be one of the three base types, '$' for scalars, '@' for arrays, and '%' for hashes. Each accessor method can be called without arguments to fetch the current value, or with an argument to set the value. ...