use Class::Struct; # declare struct, based on array: struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]); # declare struct, based on hash: struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });
package CLASS_NAME; use Class::Struct; # declare struct, based on array, implicit class name: struct( ELEMENT_NAME => ELEMENT_TYPE, ... );
package Myobj; use Class::Struct; # declare struct with four types of elements: struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );
$obj = new Myobj; # constructor
# scalar type accessor: $element_value = $obj->s; # element value $obj->s('new value'); # assign to element
# array type accessor: $ary_ref = $obj->a; # reference to whole array $ary_element_value = $obj->a(2); # array element value $obj->a(2, 'new value'); # assign to array element
# hash type accessor: $hash_ref = $obj->h; # reference to whole hash $hash_element_value = $obj->h('x'); # hash element value $obj->h('x', 'new value'); # assign to hash element
# class type accessor: $element_value = $obj->c; # object reference $obj->c->method(...); # call method of object $obj->c(new My_Other_Class); # assign a new object
The new class is given a constructor method, new, for creating struct objects.
Each element in the struct data has an accessor method, which is used to assign to the element and to fetch its value. The default accessor can be overridden by declaring a sub of the same name in the package. (See Example 2.)
Each element's type can be scalar, array, hash, or class.
struct( CLASS_NAME => [ ELEMENT_LIST ]); struct( CLASS_NAME => { ELEMENT_LIST }); struct( ELEMENT_LIST );The first and second forms explicitly identify the name of the class being created. The third form assumes the current package name as the class name.
An object of a class created by the first and third forms is based on an array, whereas an object of a class created by the second form is based on a hash. The array-based forms will be somewhat faster and smaller; the hash-based forms are more flexible.
The class created by struct must not be a subclass of another class other than UNIVERSAL.
A function named new must not be explicitly defined in a class created by struct.
The ELEMENT_LIST has the form
NAME => TYPE, ...Each name-type pair declares one element of the struct. Each element name will be defined as an accessor method unless a method by that name is explicitly defined; in the latter case, a warning is issued if the warning flag (-w) is set.
The accessor method provided by struct for an element depends
on the declared type of the element.
The accessor's argument, if any, is assigned to the element.
If the element type is '$', the value of the element (after
assignment) is returned. If the element type is '*$', a reference
to the element is returned.
With no argument, the accessor returns a reference to the element's whole array.
With one or two arguments, the first argument is an index
specifying one element of the array; the second argument, if
present, is assigned to the array element. If the element type
is '@', the accessor returns the array element value. If the
element type is '*@', a reference to the array element is
returned.
With no argument, the accessor returns a reference to the element's whole hash.
With one or two arguments, the first argument is a key specifying
one element of the hash; the second argument, if present, is
assigned to the hash element. If the element type is '%', the
accessor returns the hash element value. If the element type is
'*%', a reference to the hash element is returned.
The accessor's argument, if any, is assigned to the element. The accessor will croak if this is not an appropriate object reference.
If the element type does not start with a '*', the accessor returns the element value (after assignment). If the element type starts with a '*', a reference to the element itself is returned.
use Class::Struct;
struct( rusage => { ru_utime => timeval, # seconds ru_stime => timeval, # microseconds });
struct( timeval => [ tv_secs => '$', tv_usecs => '$', ]);
# create an object: my $t = new rusage; # $t->ru_utime and $t->ru_stime are objects of type timeval.
# set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec. $t->ru_utime->tv_secs(100); $t->ru_utime->tv_usecs(0); $t->ru_stime->tv_secs(5); $t->ru_stime->tv_usecs(0);
package MyObj; use Class::Struct;
# declare the struct struct ( 'MyObj', { count => '$', stuff => '%' } );
# override the default accessor method for 'count' sub count { my $self = shift; if ( @_ ) { die 'count must be nonnegative' if $_[0] < 0; $self->{'count'} = shift; warn "Too many args to count" if @_; } return $self->{'count'}; }
package main; $x = new MyObj; print "\$x->count(5) = ", $x->count(5), "\n"; # prints '$x->count(5) = 5'
print "\$x->count = ", $x->count, "\n"; # prints '$x->count = 5'
print "\$x->count(-5) = ", $x->count(-5), "\n"; # dies due to negative argument!
members() function removed. Documentation corrected and extended. Use of struct() in a subclass prohibited. User definition of accessor allowed. Treatment of '*' in element types corrected. Treatment of classes as element types corrected. Class name to struct() made optional. Diagnostic checks added.Originally Class::Template by Dean Roehrich.
# Template.pm --- struct/member template builder # 12mar95 # Dean Roehrich # # changes/bugs fixed since 28nov94 version: # - podified # changes/bugs fixed since 21nov94 version: # - Fixed examples. # changes/bugs fixed since 02sep94 version: # - Moved to Class::Template. # changes/bugs fixed since 20feb94 version: # - Updated to be a more proper module. # - Added "use strict". # - Bug in build_methods, was using @var when @$var needed. # - Now using my() rather than local(). # # Uses perl5 classes to create nested data types. # This is offered as one implementation of Tom Christiansen's "structs.pl" # idea.