Question

在调用BUILDARGS时，我很难正确使用MooseX :: Declare。

我正在尝试创建一个对象作为文件的接口。（具体来说，我想要一个二进制文件的接口，让我可以查看文件中的下一个字节，然后将它们关闭以进行进一步处理。）

我希望能够像这样创建其中一个对象

my $f = binary_file_buffer->new( $file_name );

然后像这样使用它

while( my $block_id = $f->peek( $id_offset, $id_length ) ) {
    $block_id = unpack_block_id( $block_id );
    $munge_block{ $block_id }->(
        $f->pop( $block_size[ $block_id ] )
    );
}

我的binary_file_buffer类定义/声明看起来像这样

use MooseX::Declare;
class binary_file_buffer {
    use FileHandle;
    use Carp;

    has _file      => ( is => 'ro', isa => 'FileHandle' );
    has _file_name => ( is => 'ro', isa => 'Str' );
    has _buff      => ( is => 'rw', isa => 'Str',  default => '' );

    method BUILDARGS ( Str $file_name ) {
      my $file = FileHandle->new( $file_name );
      carp "unable to open $file_name : $!" unless defined $file;
      $file->binmode;
      return (
        _file_name => $file_name,
        _file      => $file,
      );
    }

    # get the next n bytes from the buffer.
    method pop ( Int $len ) {
        # ... Make sure there is data in _buff
        return substr( $self->{_buff}, 0, $len, '' );
    }

    # Look around inside the buffer without changing the location for pop
    method peek ( Int $offset, Int $len ) {
        # ... Make sure there is data in _buff
        return substr( $self->{_buff}, $offset, $len );
    }
}

（缓冲区加载和管理代码我没有在这里包含。它非常直接。）

问题是，我在method声明中使用关键字BUILDARGS。因此，MooseX :: Declare期望binary_file_buffer 对象作为BUILDARGS的第一个参数。但BUILDARGS获取传递给new的参数，因此第一个参数是 string a 'binary_file_buffer'，即包的名称。因此，它在使用new创建对象时无法进行类型检查并死亡，就像我在第一个代码片段中所做的那样。（至少那是我对正在发生的事情的理解。）

我得到的错误信息是：

Validation failed for 'MooseX::Types::Structured::Tuple[MooseX::Types::Structured::Tuple[Object,Str,Bool],MooseX::Types::Structured::Dict[]]' failed with value [ [ "binary_file_buffer", "drap_iono_t1.log", 0 ], {  } ], Internal Validation Error is: Validation failed for 'MooseX::Types::Structured::Tuple[Object,Str,Bool]' failed with value [ "binary_file_buffer", "drap_iono_t1.log", 0 ] at C:/bin/perl/site/lib/MooseX/Method/Signatures/Meta/Method.pm line 445
 MooseX::Method::Signatures::Meta::Method::validate('MooseX::Method::Signatures::Meta::Method=HASH(0x2a623b4)', 'ARRAY(0x2a62764)') called at C:/bin/perl/site/lib/MooseX/Method/Signatures/Meta/Method.pm line 145
 binary_file_buffer::BUILDARGS('binary_file_buffer', 'drap_iono_t1.log') called at generated method (unknown origin) line 5
 binary_file_buffer::new('binary_file_buffer', 'drap_iono_t1.log') called at logshred.pl line 13

我喜欢method关键字为$ file_name提供的类型检查糖，但我不知道如何获取它，因为BUILDARGS在技术上不是一种方法。

MooseX :: Declare是否有办法跳过$self创建，或类似的东西？

我这样做是否适当的MooseX :: Declare方式？或者我错过了什么？

Answer 1

我认为你想要method BUILDARGS (ClassName $class: Str $filename) { ... }这样的东西，你明确地将调用者定义为ClassName $class。

Answer 2

我想你想要：

#!/use/bin/perl

use strict;
use warnings;

use MooseX::Declare;
class BinaryFile::Buffer {
    use FileHandle;
    use Carp;

    has file      => ( is => 'ro', isa => 'FileHandle');
    has file_name => ( is => 'ro', isa => 'Str');
    has _buff     => (
        is       => 'rw',
        isa      => 'Str',
        default  => '',
        init_arg => undef
    );

    sub BUILDARGS {
        my ($class, $file_name) = @_;
        my $file = FileHandle->new( $file_name ) or do {
            carp "unable to open ", $file_name, " : $!";
            return;
        };
        $file->binmode;
        return $class->SUPER::BUILDARGS(
                file_name => $file_name,
                file      => $file
        );
    }

    # get the next n bytes from the buffer.
    method pop(Int $len) {
        # ... Make sure there is data in _buff
        return substr( $self->buff, 0, $len, '' );
    }

    # Look around inside the buffer without changing the location for pop
    method peek(Int $offset, Int $len) {
        # ... Make sure there is data in _buff
        return substr( $self->buff, $offset, $len );
    }
}

my $f = BinaryFile::Buffer->new($0);

print $f->file_name, "\n";

Answer 3

这也是一种非常巧妙的方式（只是在我之前扩展答案）：

use MooseX::MultiMethods;

multi method BUILDARGS (ClassName $class: Str $filename) {

#do whatever you want to do if only a strg is passed

}

这样，如果你不打电话，MooseX :: MultiMethods会注意这一点 FileHandle-＆gt; new（$ file_name），

但是

FileHandle->new(
_filename => $file_name
);

（这是正常的语法），

它仍然可以使用！

另外，你可以（对文件名不太有用，但在其他情况下）

添加

multi method ( ClassName $class, Int $some_number ){}

这样，new现在可以处理hashrefs，整数和字符串......

哦可能性......;）

使用MooseX :: Declare创建BUILDARGS方法的正确方法是什么？

3 个答案: