class - 方法在Perl 6中返回正则表达式？

Question

我只是开始学习类(class)，所以我不懂基础知识。

我想要一种使用对象属性构造regex的方法:

class TEST {
    has Str $.str;

    method reg {
        return 
            rx/
               <<
               <[abc]> *
               $!str
               <!before foo>
              /;
    }         
}   

my $var = TEST.new(str => 'baz');
say $var.reg;

尝试运行此程序时，出现以下错误消息:

===SORRY!=== Error while compiling /home/evb/Desktop/p6/e.p6
Attribute $!str not available inside of a regex, since regexes are methods on Cursor.
Consider storing the attribute in a lexical, and using that in the regex.
at /home/evb/Desktop/p6/e.p6:11
------>                <!before foo>⏏<EOL>
    expecting any of:
        infix stopper

那么，什么是正确的方法呢？

Answer 1

看起来像这样工作:

class TEST {
    has Str $.str;

    method reg {
        my $str = $.str;
        return 
            regex {
               <<
               <[abc]> *
               $str
               <!before foo>
               }
    }         
}   

my $var = TEST.new(str => 'baz');
say $var.reg;
say "foo" ~~ $var.reg;
say "<<abaz" ~~ $var.reg

您将返回一个 anonymous regex，它可以用作实际的正则表达式，就像在最后两个句子中所做的一样。