我正在编写Perl类来从脚本中删除冗余,并且由于Perl有很多制作类的方式,我一直在努力正确地制作类。那么,有没有关于类的最佳实践示例呢?
我最大的问题是:如果模块中不应该有全局变量,那么如何在模块的sub()之间使用变量呢?就像Java中的self->foo = 10;
基本上,只要给我一个用Java或C#甚至C++编写的类,在Perl中也写出相同的代码。另外,展示如何正确使用私有、受保护和公共类变量会得到额外的积分。继承和接口可能也会对我有所帮助。
我正在编写Perl类来从脚本中删除冗余,并且由于Perl有很多制作类的方式,我一直在努力正确地制作类。那么,有没有关于类的最佳实践示例呢?
我最大的问题是:如果模块中不应该有全局变量,那么如何在模块的sub()之间使用变量呢?就像Java中的self->foo = 10;
基本上,只要给我一个用Java或C#甚至C++编写的类,在Perl中也写出相同的代码。另外,展示如何正确使用私有、受保护和公共类变量会得到额外的积分。继承和接口可能也会对我有所帮助。
创建 Perl 对象的典型方式是将哈希引用“bless”为对象。随后,对象实例可以针对其自身一组哈希键存储数据。
package SampleObject;
use strict;
use warnings;
sub new {
my ($class, %args) = @_;
return bless { %args }, $class;
}
sub sample_method {
my ($self) = @_;
print $self->{sample_data};
}
并且使用:
my $obj = SampleObject->new( sample_data => 'hello world',
more_data => 'blah blah blah' );
$obj->sample_method();
另外,也可以添加访问器/修改器方法(参见Class :: Accessor,Class :: Accessor :: Chained等),这些方法易于设置 - 这样可以更容易地验证数据并添加封装(在Perl中没有强制要求,您必须确保代码不会绕过适当的访问器/修改器并直接访问blessed哈希引用中的数据)。
Perl很容易,但我对其他语言有点生疏,稍后会更新。这是一个简单的Perl类:
#!/usr/bin/perl
package Person;
use strict;
use warnings;
use Carp;
sub new {
my $class = shift;
my $self = { @_ };
croak "bad arguments" unless defined $self->{firstname} and defined $self->{lastname};
return bless $self, $class; #this is what makes a reference into an object
}
sub name {
my $self = shift;
return "$self->{firstname} $self->{lastname}";
}
#and here is some code that uses it
package main;
my $person = Person->new(firstname => "Chas.", lastname => "Owens");
print $person->name, "\n";
以下是使用新的 Moose 风格对象编写的相同类:
#!/usr/bin/perl
package Person;
use Moose; #does use strict; use warnings; for you
has firstname => ( is => 'rw', isa => 'Str', required => 1 );
has lastname => ( is => 'rw', isa => 'Str', required => 1 );
sub name {
my $self = shift;
return $self->firstname . " " . $self->lastname;
}
#and here is some code that uses it
package main;
my $person = Person->new(firstname => "Chas.", lastname => "Owens");
print $person->name, "\n";
MooseX::Declare消除了更多代码的需求,并使代码看起来更加美观:
#!/usr/bin/perl
use MooseX::Declare;
class Person {
has firstname => ( is => 'rw', isa => 'Str', required => 1 );
has lastname => ( is => 'rw', isa => 'Str', required => 1 );
method name {
return $self->firstname . " " . $self->lastname;
}
}
#and here is some code that uses it
package main;
my $person = Person->new(firstname => "Chas.", lastname => "Owens");
print $person->name, "\n";
简单说明一下,这两个类是我编写的第一批 Moose 类。这里还有一些非常生疏的 C++ 代码(别被它划伤了,否则你需要注射破伤风疫苗):
#include <stdio.h>
#include <string.h>
class Person {
char* firstname;
char* lastname;
public:
Person(char* first, char* last) {
firstname = first;
lastname = last;
}
char* name(void) {
int len = strlen(firstname) + strlen(lastname) + 1;
char* name = new char[len];
name[0] = '\0';
strcat(name, firstname);
strcat(name, " ");
strcat(name, lastname);
return name;
}
};
int main(void) {
Person* p = new Person("Chas.", "Owens");
char* name = p->name();
printf("%s\n", name);
delete name;
delete p;
return 0;
}