perl - Perl 运行时是否有实际的派生类？

Question

我正在研究 Perl OO(Perl 新手)。我创建了一个简单的示例层次结构:
父类:

#!usr/bin/perl  
use strict;  
use warnings;  

package Objs::Employee;  

my $started;  

sub new {  
    my ($class) = @_;  
    my $cur_time = localtime;  
    my $self = {  
        started => $cur_time,  
    };
    print "Time: $cur_time \n";  
    bless $self;  
}  

sub get_started {  
    my ($class) = @_;  
    return $class->{started};  
}  

sub set_started {  
    my ($class, $value) = @_;  
    $class->{started} = $value;  
}  

1;  

child 类:

#!/usr/bin/perl  
package Objs::Manager;  
use strict;  
use warnings;  

use base qw (Objs::Employee);  

my $full_name;  

sub new {  
    my ($class, $name) = @_;  
    my $self = $class->SUPER::new();  
    $self->{full_name} = $name;  
    return $self;     
}  

1;  

我尝试按如下方式对其进行测试:

#!/usr/bin/perl  
use strict;  
use warnings;  


use Objs::Manager;  

my $emp = Objs::Manager->new('John Smith');  
use Data::Dumper;  
print Dumper($emp); 

结果:

时间:2013年9月29日星期日12:56:29

$VAR1 = bless( {
                 'started' => 'Sun Sep 29 12:56:29 2013',
                 'full_name' => 'John Smith'
               }, 'Objs::Employee' );

问题:为什么转储中报告的对象是 Obj::Employee 而不是 Obj::Manager？
我调用经理的新人。

Answer 1

bless 总是使用两个参数, 如 $class告诉哪个包应该被祝福。如 $class省略，则使用当前包。

bless $self, $class; 

输出

$VAR1 = bless( {
             'started' => 'Sun Sep 29 13:24:26 2013',
             'full_name' => 'John Smith'
           }, 'Objs::Manager' );

来自 perldoc -f bless :

Always use the two-argument version if a derived class might inherit the function doing the blessing