perl - 如何创建 Perl 类？

Question

我正在编写 Perl 类以从脚本中删除冗余，并且由于 Perl 有很多方法可以制作类，所以我一直无法正确制作类。那么有没有人有一个类(class)的最佳实践例子？

我最大的问题是模块中是否不应该有全局变量，如何在模块中的 sub() 中使用变量？像 Java self->foo = 10;

基本上只需给我一个用 Java 或 C# 甚至 C++ 编写的类，然后用 Perl 编写相同的类。还展示了如何正确处理私有(private)、 protected 和公共(public)类变量的额外要点。我猜继承和接口(interface)会有所帮助。

Answer 1

嗯，Perl 很简单，但是我对其他语言很生疏，所以我会稍微更新一下。这是一个普通的 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";

这是使用新的 Moose 样式对象编写的同一个类:

#!/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 消除了对更多代码的需求，并使事情看起来不错:

#!/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";

快速说明，这两个类是我写过的前两个 Moose 类。这里有一些非常生锈的 C++ 代码(不要在上面割伤自己，否则你需要打破伤风疫苗):

#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;
}