SUPER :: methods在Perl中测试分支分配

Question

我即将完成学习Intermediate Perl书。

在第18章对象销毁介绍以下DESTROY方法定义：

# lib/Animal.pm 
package Animal { 
    # ... 
    sub DESTROY { 
    my $self = shift; 
    if ($self->{temp_filename}){ 
     my $fh = $self->{temp_fh}; 
     close $fh; 
     unlink $self->{temp_filename}; 
    } 
    print '[', $self->name, " has died.]\n"; 
    } 
# ... 
} 

# lib/Horse.pm 
package Horse { 
    use parent qw(Animal) 
    # ... 
    sub DESTROY { 
    my $self = shift; 
    $self->SUPER::DESTROY if $self->can('SUPER::DESTROY'); 
    print "[", $self->name, " has gone off to the glue factory.]\n"; 
    } 
# ... 
} 

几个后不成功的尝试，我写了基于this answer这个测试：

# t/Horse.t 
#!perl -T 

use strict; 
use warnings; 
use Test::More tests => 6; 
use Test::Output; 
# some other tests 

# test DESTROY() when SUPER::DESTROY is not defined; 
{ 
    my $tv_horse = Horse->named('Mr. Ed'); 
    stdout_is(sub { $tv_horse->DESTROY }, "[Mr. Ed has died.]\n[Mr. Ed has gone off to the glue factory.]\n", 
     'Horse DESTROY() when SUPER::DESTROY is defined'); 
} 

{ 
    my $tv_horse = Horse->named('Mr. Ed'); 
    sub Animal::DESTROY { undef } 
    stdout_is(sub { $tv_horse->DESTROY }, "[Mr. Ed has gone off to the glue factory.]\n", 
     'Horse DESTROY() when SUPER::DESTROY is not defined'); 
} 

我无法测试由于方法重定义sub Animal::DESTROY { undef }也影响前一个程序段中的测试，所以两种情况下的输出均正确。

您是否知道确保方法重新定义按预期工作的方法？

感谢

Answer 1

这应该设置移除/重新定义子程序只有等到封闭块结束，

{ 
    # not needed when removing method 
    # no warnings 'redefine'; 

    my $tv_horse = Horse->named('Mr. Ed'); 
    # returns undef 
    # local *Animal::DESTROY = sub { undef }; 

    # remove the mothod until end of the enclosing block 
    local *Animal::DESTROY; 

    # .. 
}