在perl中的子例程中声明全局变量

I was wondering if it's possible to declare a global variable within a subroutine in Perl so that I can use that variable in a hooked void function, but limiting the damaging effects of the global by having it declared in a subroutine.

我想知道是否可以在Perl子例程中声明一个全局变量，这样我就可以在一个连接的void函数中使用这个变量，但是通过在子例程中声明它来限制全局变量的破坏性影响。

So the subroutine uses XML::Parser to collect the IDs of a bunch of elements, in a manner similar to:

因此，子例程使用XML::Parser来收集一系列元素的id，其方式类似于:

sub getRecipeIDs {
    my $recipe = shift;
    my @elements = ();

    my $parser = new XML::Parser(Style => 'Tree',
        Handlers => {
            Start => sub {
                my ($expat, $element, %attrs) = @_;
                if ($element eq 'recipe') {
                    push @elements, $attrs{id};
                }
        }});

    $parser->parse($recipe);

    return @elements;
}

I'm also using strict in my script.

我在脚本中也使用了strict。

So I want to declare @elements in such a way that it is local to getRecipeIDs but is visible to the anonymous subroutine.

因此，我想以这样的方式声明@元素，它是getrecipeid的局部变量，但对匿名子例程是可见的。

Thanks for your time, any help is greatly appreciated.

谢谢您的时间，任何帮助都是非常感谢的。

3 个解决方案

#1

It should already work the way in which you've written your example. What you're doing with "my $func = sub { ... }" is you create a closure which has access to the enclosing scope's variables -- in this case @elements.

它应该已经按照您编写示例的方式工作了。你用“我的$func = sub{…”}“您是否创建了一个闭包，它可以访问封闭范围的变量——在本例中是@elements。

#2

my is fine. Lexical variables are visible in nested scopes, such as anonymous subroutines.

我很好。在嵌套范围(如匿名子例程)中可以看到词汇变量。

Your code should therefore work as-is.

因此，您的代码应该按原样工作。

#3

Your code should work fine as it stands

您的代码应该能够正常工作

Despite the depth of the anonymous subroutine, its scope includes the lexical array @elements and it can access it freely

尽管匿名子例程的深度很大，但它的范围包括lexical数组@elements，并且可以*访问它

Furthermore the subroutine counts as a reference to the array, so it will not be garbage collected when it goes out of scope at the end of the call to getRecipeIDs

此外，子例程计数作为对数组的引用，因此在对getrecipeid的调用结束时，当它超出范围时，不会被垃圾收集

#1