我可以在 Perl 5 中为字符串创建文件句柄，我如何在 Perl 6 中做到这一点? [英] I can create filehandles to strings in Perl 5, how do I do it in Perl 6?

问题描述

在 Perl 5 中，我可以创建一个字符串的文件句柄，并从字符串中读取或写入，就像它是一个文件一样.这非常适合处理测试或模板.

In Perl 5, I can create a filehandle to a string and read or write from the string as if it were a file. This is great for working with tests or templates.

例如:

use v5.10; use strict; use warnings;

my $text = "A\nB\nC\n";

open(my $fh, '<', \$text);

while(my $line = readline($fh)){
    print $line;
}

我怎样才能在 Perl 6 中做到这一点?以下不适用于 Perl 6(至少不适用于我在 MoarVM 2015.01 来自 2015 年 1 月发布的 Rakudo Star64 位 CentOS 6.5):

How can I do that in Perl 6? The following doesn't work for Perl 6 (at least not for my instance of Perl6 running on MoarVM 2015.01 from the January 2015 release of Rakudo Star on 64-bit CentOS 6.5):

# Warning: This code does not work
use v6;

my $text = "A\nB\nC\n";

my $fh = $text;

while (my $line = $fh.get ) {
    $line.say;
}
# Warning: Example of nonfunctional code

我收到错误消息:

No such method 'get' for invocant of type 'Str'
   in block <unit> at string_fh.p6:8

Perl5 的 open(my $fh, '<', \$text) 与 Perl6 的 my $fh = $text; 不一样并不奇怪>.所以问题是:如何从 Perl 6 中的字符串创建虚拟文件句柄，如 Perl 5 中的 open(my $fh, '<', \$str) ?或者是尚未实施的内容?

It's not very surprising that Perl5's open(my $fh, '<', \$text) is not the same as Perl6's my $fh = $text;. So the question is: How does one create a virtual file handle from a string in Perl 6 like open(my $fh, '<', \$str) in Perl 5? Or is that something that has yet to be implemented?

更新(在 Perl 5 中写入文件句柄)

UPDATE (writing to a filehandle in Perl 5)

同样，您可以在 Perl 5 中写入字符串文件句柄:

Likewise, you can write to string filehandles in Perl 5:

use v5.10; use strict; use warnings;

 my $text = "";
 open(my $fh, '>', \$text);

 print $fh "A";
 print $fh "B";
 print $fh "C";

 print "My string is '$text'\n";

输出:

 My string is 'ABC'

我还没有在 Perl 6 中看到任何类似的东西.

I haven't seen anything remotely similar in Perl 6, yet.

推荐答案

阅读

逐行阅读的惯用方式是 .lines方法，在 Str 和 IO::Handle 上都可用.

Reading

The idiomatic way to read line-by-line is the .lines method, which is available on both Str and IO::Handle.

它返回一个惰性列表，您可以将其传递给 for，如

It returns a lazy list which you can pass on to for, as in

my $text = "A\nB\nC\n";

for $text.lines -> $line {
     # do something with $line
}

写作

my $scalar;
my $fh = IO::Handle.new but
         role {
             method print (*@stuff) { $scalar ~= @stuff };
             method print-nl        { $scalar ~= "\n" }
         };

$fh.say("OH HAI");
$fh.say("bai bai");

say $scalar
# OH HAI
# bai bai

(改编自 #perl6，感谢 Carl Mäsak.)

(Adapted from #perl6, thanks to Carl Mäsak.)

如果您需要更复杂的机制来伪造文件句柄，请使用 IO::Capture::Simple 和 IO::String 在 生态系统.

If you need a more sophisticated mechanism to fake file handles, there's IO::Capture::Simple and IO::String in the ecosystem.

例如:

use IO::Capture::Simple;
my $result;
capture_stdout_on($result);
say "Howdy there!";
say "Hai!";
capture_stdout_off();
say "Captured string:\n" ~$result;

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