如何在Perl中的基类和子类之间共享变量？ [英] How can I share variables between a base class and subclass in Perl?

问题描述

我有一个这样的基类：

package MyClass;

use vars qw/$ME list of vars/;
use Exporter;
@ISA = qw/Exporter/;
@EXPORT_OK = qw/ many variables & functions/;
%EXPORT_TAGS = (all => \@EXPORT_OK );

sub my_method {

}
sub other_methods etc {

}

--- more code---

我想对 MyClass 进行子类化

package MySubclass;

use MyClass;
use vars qw/@ISA/;
@ISA = 'MyClass';

sub my_method {

--- new method

}

我想将其称为 MySubclass ，就像我原来的 MyClass ，并且仍然可以从导出器访问所有变量和函数。但是，我无法从原始类 MyClass 正确导出 Exporter 变量。我是否需要在子类中再次运行 Exporter ？

And I want to call this MySubclass like I would the original MyClass, and still have access to all of the variables and functions from Exporter. However I am having problems getting the Exporter variables from the original class, MyClass, to export correctly. Do I need to run Exporter again inside the subclass? That seems redundant and unclear.

示例文件：

#!/usr/bin/perl

use MySubclass qw/$ME/;

-- rest of code

但是尝试时出现编译错误导入 $ ME 变量。有建议吗？

But I get compile errors when I try to import the $ME variable. Any suggestions?

推荐答案

您实际上并没有从<<继承$ MySubclass code> MyClass 完全- MySubClass 是 MyClass <的用户/ code>。您正在执行的操作是覆盖 MyClass 的行为，但是如果您将其视为继承，则只会混淆自己，因为它不是（例如：您的构造函数在哪里？）我无法弄清楚您要做什么，直到我忽略了代码正在做的所有事情，而只是阅读了您对要发生的事情的描述。

You're not actually inheriting MySubclass from MyClass at all -- MySubClass is a user of MyClass. What you're doing is overriding a bit of behaviour from MyClass, but you will only confuse yourself if you think of this as inheritance, because it isn't (for example: where is your constructor?) I couldn't figure out what you were trying to do until I ignored everything the code was doing and just read your description of what you want to have happen.

好的，所以您有一个导入一些符号的类-一些函数和一些变量：

Okay, so you have a class which imports some symbols - some functions, and some variables:

package MyClass;
use strict;
use warnings;

use Exporter 'import';    # gives you Exporter's import() method directly
our @EXPORT_OK = qw/ many variables & functions/;
our %EXPORT_TAGS = (all => \@EXPORT_OK );
our ($ME, $list, $of, $vars);

sub my_func {

}
sub other_func {

}
1;

然后您来编写一个从MyClass导入一切的类，然后再次全部导入，但将一个函数换成另一个：

and then you come along and write a class which imports everything from MyClass, imports it all back out again, but swaps out one function for another one:

package MyBetterclass;
use strict;
use warnings;
use Exporter 'import';    # gives you Exporter's import() method directly
our @EXPORT_OK = qw/ many variables & functions /;
our %EXPORT_TAGS = (all => \@EXPORT_OK );
use MyClass ':all';

sub my_func {
    # new definition   
}
1;

就是这样！请注意，我启用了严格的检查和警告，并更改了实际起作用的方法的名称。
此外，我没有使用 use vars （文档说它已经过时了，所以如果您仍然想在不了解其机制的情况下使用它，那将是一个很大的警告。）

That's it! Note that I enabled strict checking and warnings, and changed the names of the "methods" that are actually functions. Additionally, I did not use use vars (the documentation says it's obsolete, so that's a big red flag if you still want to use it without understanding its mechanics).

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