Moose和Roles方法修改器(Moose and Roles method modifers)

Moose和Roles方法修改器(Moose and Roles method modifers)

可以在Role中使用after修饰符来通过构建器方法填充在使用类中的必需属性吗？

package A::Role; use Moose::Role; use IO::File; use Carp; requires 'properties_file'; after 'properties_file' => sub { my $self = shift; $self->_check_prop_file(); $self->_read_file(); };

消费类：

package A::B::C; use Moose; use Carp; use Moose; use Carp; use HA::Connection::SSH; use constant { ... }; has 'properties_file' => ( is => 'ro', isa => 'Str', builder => '_build_current_data'); with 'A::Role'; sub _build_current_data { ... }

It is possible to use an after modifier in a Role for a required attribute that is populated in the consuming class via a builder method?

package A::Role; use Moose::Role; use IO::File; use Carp; requires 'properties_file'; after 'properties_file' => sub { my $self = shift; $self->_check_prop_file(); $self->_read_file(); };

Consuming class:

package A::B::C; use Moose; use Carp; use Moose; use Carp; use HA::Connection::SSH; use constant { ... }; has 'properties_file' => ( is => 'ro', isa => 'Str', builder => '_build_current_data'); with 'A::Role'; sub _build_current_data { ... }

最满意答案

回答你的问题：是的，你可以。 您已经完成了在声明属性后使用角色以便生成访问器方法的关键部分。

因此，您提供的代码将按照您期望的顺序执行： -

my $c = A::B::C->new; # 'properties_file' is built by _build_current_data() my $filename = $c->properties_file; # _check_prop_file() and _read_file() are executed (but before $filename is assigned)

但是，通过获取 properties_file调用属性文件的检查和读取似乎很奇怪。 如果您只想在构造后自动检查和读取属性文件，则角色可以提供要在类中使用的BUILD方法。 （ BUILD后执行BUILD ，因此properties_file将初始化。）

sub BUILD { my $self = shift; $self->_check_prop_file(); $self->_read_file(); return; }

To answer your question: Yes you can. You've already done the crucial part which was to consume the role after declaring the attribute so that the accessor method is generated.

So the code that you supplied would execute in the sequence that you would expect:-

my $c = A::B::C->new; # 'properties_file' is built by _build_current_data() my $filename = $c->properties_file; # _check_prop_file() and _read_file() are executed (but before $filename is assigned)

However, it does seem strange that you invoke the checking and reading of the properties file by getting properties_file. If you just want the properties file to be checked and read automatically after construction, the role could supply a BUILD method to be consumed into the class. (BUILD is executed after construction, so properties_file will be initialised already.)

sub BUILD { my $self = shift; $self->_check_prop_file(); $self->_read_file(); return; }Moose和Roles方法修改器(Moose and Roles method modifers)

可以在Role中使用after修饰符来通过构建器方法填充在使用类中的必需属性吗？

package A::Role; use Moose::Role; use IO::File; use Carp; requires 'properties_file'; after 'properties_file' => sub { my $self = shift; $self->_check_prop_file(); $self->_read_file(); };

消费类：

package A::B::C; use Moose; use Carp; use Moose; use Carp; use HA::Connection::SSH; use constant { ... }; has 'properties_file' => ( is => 'ro', isa => 'Str', builder => '_build_current_data'); with 'A::Role'; sub _build_current_data { ... }

It is possible to use an after modifier in a Role for a required attribute that is populated in the consuming class via a builder method?

package A::Role; use Moose::Role; use IO::File; use Carp; requires 'properties_file'; after 'properties_file' => sub { my $self = shift; $self->_check_prop_file(); $self->_read_file(); };

Consuming class:

package A::B::C; use Moose; use Carp; use Moose; use Carp; use HA::Connection::SSH; use constant { ... }; has 'properties_file' => ( is => 'ro', isa => 'Str', builder => '_build_current_data'); with 'A::Role'; sub _build_current_data { ... }

最满意答案

回答你的问题：是的，你可以。 您已经完成了在声明属性后使用角色以便生成访问器方法的关键部分。

因此，您提供的代码将按照您期望的顺序执行： -

my $c = A::B::C->new; # 'properties_file' is built by _build_current_data() my $filename = $c->properties_file; # _check_prop_file() and _read_file() are executed (but before $filename is assigned)

但是，通过获取 properties_file调用属性文件的检查和读取似乎很奇怪。 如果您只想在构造后自动检查和读取属性文件，则角色可以提供要在类中使用的BUILD方法。 （ BUILD后执行BUILD ，因此properties_file将初始化。）

sub BUILD { my $self = shift; $self->_check_prop_file(); $self->_read_file(); return; }

To answer your question: Yes you can. You've already done the crucial part which was to consume the role after declaring the attribute so that the accessor method is generated.

So the code that you supplied would execute in the sequence that you would expect:-

my $c = A::B::C->new; # 'properties_file' is built by _build_current_data() my $filename = $c->properties_file; # _check_prop_file() and _read_file() are executed (but before $filename is assigned)

However, it does seem strange that you invoke the checking and reading of the properties file by getting properties_file. If you just want the properties file to be checked and read automatically after construction, the role could supply a BUILD method to be consumed into the class. (BUILD is executed after construction, so properties_file will be initialised already.)

sub BUILD { my $self = shift; $self->_check_prop_file(); $self->_read_file(); return; }