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32.6. Class::Struct
use Class::Struct;
struct Manager => { # Creates a Manager->new() constructor.
name => ''$'', # Now name() method accesses a scalar value.
salary => ''$'', # And so does salary().
started => ''$'', # And so does started().
};
struct Shoppe => {# Creates a Shoppe->new() constructor.
owner => ''$'',# Now owner() method accesses a scalar.
addrs => ''@'', # And addrs() method accesses an array.
stock => ''%'',# And stock() method accesses a hash.
boss => ''Manager'',
# Initializes with Manager->new().
};
$store = Shoppe->new();
$store->owner(''Abdul Alhazred'');
$store->addrs(0, ''Miskatonic University'');
$store->addrs(1, ''Innsmouth, Mass.'');
$store->stock("books", 208);
$store->stock("charms", 3);
$store->stock("potions", "none");
$store->boss->name(''Prof L. P. Haitch'');
$store->boss->salary(''madness'');
$store->boss->started(scalar localtime);
The Class::Struct module provides a way to
"declare" a class as having objects whose fields are of a specific
type. The function that does this is called
struct. Because structures or records are not base
types in Perl, each time you want to create a class to provide a
record-like data object, you have to define a constructor method along
with accessor methods for each data field, sometimes called "wrapper"
methods. The Class::Struct module''s
struct function alleviates this tedium by creating
a class for you on the fly. You just tell it what data members should
exist and their types. The function creates a constructor method
named new in the package specified by the first
argument, plus an attribute accessor method for each member, as
specified by the second argument, which should be a hash reference.Field types are specified as either a built-in type using the
customary "$", "@",
"%", and "&" symbols, or as
another class using the class name. The type of each field will be
enforced when you try to set the value.
Many standard modules use Class::Struct to create
their objects and accessors, including Net::hostent
and User::pwent, whose source you can look at as a
model. See also the CPAN modules Tie::SecureHash
and Class::Multimethods for more elaborate
approaches to autogeneration of classes and accessor methods. See the
section "Managing Instance Data" in Chapter 12, "Objects".