Question

我在MooseX::Declare中使用BUILD方法时遇到了问题。如果我说：

#!/usr/bin/perl

use MooseX::Declare;

class Foo {
    has foo => (is => "rw", isa => "Str", default => "foo");

    method BUILD {
        print "I was called\n";
    }
}

Foo->new;

我收到以下不太有用的错误消息：

Reference found where even-sized list expected at /Users/cowens/perl5/lib/perl5/MooseX/Method/Signatures/Meta/Method.pm line 335.
Validation failed for 'MooseX::Types::Structured::Tuple[MooseX::Types::Structured::Tuple[Object],MooseX::Types::Structured::Dict[]]' failed with value [ [ Foo=HASH(0x804b20) ], { HASH(0x8049e0) => undef } ], Internal Validation Error is: Validation failed for 'MooseX::Types::Structured::Dict[]' failed with value { HASH(0x8049e0) => undef } at /Users/cowens/perl5/lib/perl5/MooseX/Method/Signatures/Meta/Method.pm line 365
        MooseX::Method::Signatures::Meta::Method::validate('MooseX::Method::Signatures::Meta::Method=HASH(0xb8aab0)', 'ARRAY(0xb8ab30)') called at /Users/cowens/perl5/lib/perl5/MooseX/Method/Signatures/Meta/Method.pm line 139
        Foo::BUILD('Foo=HASH(0x804b20)', 'HASH(0x8049e0)') called at generated method (unknown origin) line 25
        Foo::new('Foo') called at test.pl line 13

但如果我说：

#!/usr/bin/perl

use MooseX::Declare;

class Foo {
    has foo => (is => "rw", isa => "Str", default => "foo");

    sub BUILD {
        my $self = shift;
        print "I was called\n";
    }
}

Foo->new;

一切都运行得很好（但是其余的代码很丑陋而且不合适。）

Answer 1

如果你不需要，

BUILD需要一个arg，只需说：

method BUILD($) { ... }

Answer 2

它失败了因为BUILD需要一个arg方法签名。默认情况下，MooseX::Declare会创建一个与BUILD调用方式不兼容的签名。（细节对我来说很模糊。）我知道因为我遇到过类似的错误一次。我当然同意错误信息可能更具启发性;很多Moose的东西都是如此。

无论如何，我让它像这样工作：

use MooseX::Declare;

class Foo {
    has foo => (is => "rw", isa => "Str", default => "foo");

    method BUILD(Item $href) {
        print "I was called\n";
    }
}

Foo->new;

希望有所帮助。

您可以摆弄签名并尝试更具体的类型;我认为Moose发送了一个尚未完成的对象的hashref作为参数。

Answer 3

Perl理解sub，因此可以输入当前包的符号表。＆amp; Foo :: BUILD，在Devel::Declare之后，其他魔法从类闭包中创建了一个包范围。

Moose专门查找BUILD子，以允许您操作构造函数逻辑。我的猜测（虽然我还没有完全追溯）是MooseX模块不会像Moose那样做。因此，本机BUILD将永远传递给Moose魔法以确定构造函数逻辑。

另一方面，method关键字在元类结构中创建方法更具有Devel::Declare魔力。

在MooseX :: Declare中创建BUILD方法的正确方法是什么？

3 个答案: