NAME
Attribute::Types - Attributes that confer type on variables
VERSION
This document describes version 0.10 of Attribute::Types, released May 10, 2001.
SYNOPSIS
use Attribute::Types;
my $count : INTEGER; # Can only store an integer
my $date : INTEGER(1..31); # Can only store an int between 1..31
my $value : NUMBER; # Can only store a number
my $score : NUMBER(0.1..9.9); # Can only store a num between 0.1..9.9
my @rain : NUMBER; # Elements can only store numbers
my %vars : SCALAR; # Entries can only store scalar refs
my %handler : CODE; # Entries can only store sub refs
my $arr : ARRAY; # Can only store array ref
my @hashes : HASH; # Elements can only store hash refs
my $glob : GLOB; # Can only store a typeglob ref
my $pattern : REGEX; # Can only store a qr'd regex
my $ref2 : REF; # Can only store a meta-reference
my $obj : Type(My::Class); # Can only store objects of (or
# derived from) the specified class
my $x : Type(/good|bad|ugly/); # Can only store strings matching
# the specified regex
sub odd { no warnings; $_[0]%2 }
my $guarded : Type(&odd); # Can only store values for which
# odd($value) returns true
$date = 23; # okay
$date = 32; # KABOOM!
$rain[1] = 121.7; # okay
$rain[1] = "lots"; # KABOOM!
$x = 'very good'; # okay
$x = 'excellent'; # KABOOM!
package My::Class::Der;
use base 'My::Class';
$obj = My::Class->new(); # okay
$obj = My::Class::Der->new(); # okay
$obj = Other::Class->new(); # KABOOM!
$guarded = 1; # okay
$guarded = 2; # KABOOM!DESCRIPTION
The Attribute::Types module provides 10 universally accessible attributes that can be used to create variables that accept assignments of only specific types of data.
The attributes are:
INTEGER-
Indicates that the associated scalar, or the elements of the associated array, or the entries of the associated hash can only contain integer values (those values that are internally represented as actual numbers (or may be converted to actual numbers without generating a warning), and for which
int($value)==$value).The attribute may also be specified with a range of integer values, indicating a further restriction on the values the associated variable can store. For example:
my $x1 : INTEGER(1..100); # Any int between 1 and 100 my $x2 : INTEGER(-10..10); # Any ine between -10 and 10 my $x3 : INTEGER(0..); # Any positive int my $x4 : INTEGER(..99); # Any int < 100 (including negatives) NUMBER-
Indicates that the associated scalar, or the elements of the associated array, or the entries of the associated hash can only contain values that are internally represented by (or silently convertible to) valid Perl numbers.
The attribute may also be specified with a range of numerical values, indicating a further restriction on the values the associated variable can store. For example:
my $x1 : NUMBER(1.0..100.0); # Any number between 1 and 100 my $x2 : NUMBER(-10..10); # Any number between -10 and 10 my $x3 : NUMBER(0..); # Any positive number my $x4 : NUMBER(..99.9); # Any number < 99.9 (incl. negatives) SCALAR-
Indicates that the associated scalar, or the elements of the associated array, or the entries of the associated hash can only contain references to scalars (i.e. only values for which
ref($value) eq 'SCALAR'). ARRAY-
Indicates that the associated variable can only contain references to arrays (i.e. only values for which
ref($value) eq 'ARRAY'). HASH-
Indicates that the associated variable can only contain references to hashes (i.e. only values for which
ref($value) eq 'HASH'). CODE-
Indicates that the associated variable can only contain references to subroutines (i.e. only values for which
ref($value) eq 'CODE'). GLOB-
Indicates that the associated variable can only contain references to typeglobs (i.e. only values for which
ref($value) eq 'GLOB'). REF-
Indicates that the associated variable can only contain references to other references (i.e. only values for which
ref($value) eq 'REF'). REGEX-
Indicates that the associated variable can only contain references to precompiled regular expressions (i.e. only values for which
ref($value) eq 'Regexp'). Type-
Used to specify class-wise or generic storage constraints on a variable. There are three permitted syntaxes:
Type(Class::Name)-
Indicates that the associated variable can only contain references to objects belonging to the specified class, or to one of its derived classes.
Type(/pattern/)-
Indicates that the associated variable can only contain values that successfully match the specified pattern.
Type(&subname)-
Indicates that the associated variable can only contain values for which the specified subroutine returns true when passed the value as its first argument.
Note that anonymous subroutines cannot be used in this context (they are run-time phenomena and types have to be set up at compile-time).
If the module is imported with a list of attribute names:
use Attribute::Types qw(INTEGER HASH);then only those attributes can be used to specify types.
CAVEAT
The type checking set up by this module is run-time type-checking. That is, the validity of an assignment is only checked when the assignment operation is actually performed, not when it is compiled.
DIAGNOSTICS
Cannot assign value to type variable-
The value being assigned is not consistent with the declared type of the variable.
Can't specify type attribute for CODE-
Subroutines cannot be typed using the Attribute::Types attributes.
Invalid type specifier: Type(garbage)-
The
Type(...)attribute can only be specified with a class name, a pattern (in /.../), or a subroutine name.
BLAME
This is all Nat Torkington's idea.
AUTHOR
Damian Conway (damian@conway.org)
BUGS AND IRRITATIONS
There are undoubtedly serious bugs lurking somewhere in this code :-) Bug reports and other feedback are most welcome.
COPYRIGHT
Copyright (c) 2001, Damian Conway. All Rights Reserved.
This module is free software. It may be used, redistributed
and/or modified under the same terms as Perl itself.