如何修改传递给子例程引用的标量引用？
我有一个将文档转换为不同格式的函数，然后根据类型文档调用另一个函数。除了需要进行一些清理的 HTML 文档之外，其他所有内容都非常简单，而且清理工作根据其来源而有所不同。所以我有一个想法，我可以将对子例程的引用传递给转换函数，以便调用者有机会修改 HTML，有点像这样（我不在工作，所以这不是复制粘贴的） ：
package Converter;
...
sub convert
{
my ($self, $filename, $coderef) = @_;
if ($filename =~ /html?$/i) {
$self->_convert_html($filename, $coderef);
}
}
sub _convert_html
{
my ($self, $filename, $coderef) = @_;
my $html = $self->slurp($filename);
$coderef->(\$html); #this modifies the html
$self->save_to_file($filename, $html);
}
然后被调用：
Converter->new->convert("./whatever.html", sub { s/<html>/<xml>/i });
我已经尝试了几种不同的方法，但我不断收到“在替换中使用未初始化的值（s///）”。有什么办法可以做我想做的事情吗？
谢谢
I have a function to convert documents into different formats, which then calls another function based on the type document. It's pretty straight forward for everything aside from HTML documents which require a bit of cleaning up, and that cleaning up is different based on where it's come from. So I had the idea that I could pass a reference to a subroutine to the convert function so the caller has the opportunity to modify the HTML, kinda like so (I'm not at work so this isn't copy-and-pasted):
package Converter;
...
sub convert
{
my ($self, $filename, $coderef) = @_;
if ($filename =~ /html?$/i) {
$self->_convert_html($filename, $coderef);
}
}
sub _convert_html
{
my ($self, $filename, $coderef) = @_;
my $html = $self->slurp($filename);
$coderef->(\$html); #this modifies the html
$self->save_to_file($filename, $html);
}
which is then called by:
Converter->new->convert("./whatever.html", sub { s/<html>/<xml>/i });
I've tried a couple of different things along these lines but I keep on getting 'Use of uninitialized value in substitution (s///)'. Is there any way of doing what I'm trying to do?
Thanks
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如果是我，我会避免修改标量引用而只返回更改后的值：
但是，如果您想修改子参数，则值得知道所有子参数在 Perl 中都是按引用传递的（
@_是子调用参数的别名）。所以你的转换子可以看起来像：但是如果你真的想对
$_进行操作，就像你想要的代码示例中那样，你需要使_convert_html()看起来例如：for是正确本地化$_的简单方法。您还可以这样做：If it were me, I would avoid modifying the scalar ref and just return the changed value:
However, if you want to modify a sub's arguments, it is worth knowing that all sub arguments are pass-by-reference in Perl (the elements of
@_are aliased to the arguments of the sub call). So your conversion sub can look like:But if you really want to operate on
$_, like you have in your desired code example, you need to make_convert_html()look like:The
foris an easy way to properly localize$_. You can also do:请记住，
s///本身对$_进行操作，但是您的标量引用将作为参数传递到您的回调子中，因此位于>@_数组。因此，您可以将回调 sub 更改为如下所示：
或者，您可以利用 Perl 子例程参数的别名性质，并直接修改它：
然后
（这实际上会修改原始字符串，只要参数是标量变量而不是文字字符串。）
Remember that an
s///by itself operates on$_, but your scalar reference is being passed into your callback sub as an argument, and is therefore in the@_array.So you can just change your callback sub to something like this:
Or, you could take advantage of the aliased nature of Perl subroutine arguments, and modify it directly:
and then
(This will actually modify the original string, as long as the argument is a scalar variable and not a literal string.)
试试这个：
您收到未初始化值警告，因为没有为替换提供任何可操作的内容（
$_在其范围内未定义）。您需要告诉它在哪里可以找到它的值（在@_中，作为参考）。如果你想变得更奇特，你可以让 coderef 默认对其所有参数进行操作：
Try this:
You are getting an uninitialized value warning because the substitution isn't being given anything to operate on (
$_is undefined in its scope). You need to tell it where to find its value (in@_, as a reference).If you want to be fancy you could make the coderef operate on all its args by default: