本文介绍了如何处理Moose中的可选参数?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我目前正在使用"Moose"软件包开始Perl OOP.
I'm currently starting with Perl OOP using the "Moose" package.
编译器抱怨它无法在Parser.pm第16行修改非左值子例程调用."
The compiler complains that it "Can't modify non-lvalue subroutine call at Parser.pm line 16."
我不太明白为什么我不能只分配一个新对象.我猜想有一种更好或更有效的方法来用Moose做可选参数吗?
I don't quite understand why I can't just assign a new object. I guess there is a better or more valid way to do optional parameters with Moose?
#!/usr/bin/perl -w
package Parser;
use Moose;
require URLSpan;
require WWW::Mechanize;
has 'urlspan' => (is => 'rw', isa => 'URLSpan', required => 1);
has 'mech' => (is => 'rw', isa => 'WWW::Mechanize');
sub BUILD {
my $self = shift;
if(!$self->mech) {
warn("no Mech set for " . $self->urlspan->name);
$self->mech = WWW::Mechanize->new(agent => 'Mozilla/5.0 (Windows; U; Windows NT 6.0; de; rv:1.9.0.6) Gecko/2009011913 Firefox/3.0.4',
stack_depth => 1
); #line 16
}
}
推荐答案
$self->mech
是方法调用;您不能真正将其像C结构中的字段一样对待.如果要设置它,则需要将新对象传递给它.
$self->mech
is a method call; you can't really treat it like a field in a C struct. If you want to set it, you need to pass the new object to it.
$self->mech(
WWW::Mechanize->new(
agent => 'xyz',
stack_depth => 1
)
);
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