析构函数(DESTROY 方法)

beyes

Perl 维护了对象的引用信息，在这些引用计数为 0 时会自动销毁对象，当然在程序退出时，所有的对象都将销毁。

Perl 提供了 DESTROY 方法，它允许我们在对象被销毁前利用该即将被销毁的对象做点什么。

自定义一个名为 Employee.pm 的模块，里面代码为：
[code=perl]package Employee;

sub new {
        my $class = shift;
        $ref = {};
        bless ($ref, $class);
        return $ref;
}

sub DESTROY {
        my $self = shift;
        print "Employee $self->{Name} is being destroyed.\n";
}

1;
[/mw_shl_code]
下面脚本使用该模块：
[code=perl]#!/usr/bin/perl

use Employee;

my $emp1 = Employee->new;

#$emp2在代码块中,退出时 my 变量失去作用域,对象也被销毁
#此时会调用DESTROY方法
{
        my $emp2 = Employee->new;
        $emp2->{"Name"} = "Christian Dobbins";
        print "\t\t$emp2->{'Name'}\n";
}




my $emp3 = Employee->new;

$emp1->{"Name"} = "Dan Savage";
$emp3->{"Name"} = "Willie Rogers";

print "Here are our remaining employee:\n";
print "\t\t$emp1->{'Name'}\n";
print "\t\t$emp3->{'Name'}\n";[/mw_shl_code]
运行输出：

$ ./des.pl
                Christian Dobbins
Employee Christian Dobbins is being destroyed.
Here are our remaining employee:
                Dan Savage
                Willie Rogers
Employee Dan Savage is being destroyed.
Employee Willie Rogers is being destroyed.