Question

我们可以使用AUTOLOAD捕获未定义的方法，有没有办法在类实例中捕获未定义的变量？

package Example;
sub new {
    my ($class) = @_;
    my $self = {};
    bless($self, $class);
    return $self;
}
sub AUTOLOAD {
    print("hello\n");
}


use Example;
my $exp = Example->new();
$exp->methodname; # prints "hello"
$exp->{fieldname}; # currently undefined

Answer 1

您的课程可以打包tied hash

package Example::Tie;
sub TIEHASH {
    my ($pkg,@list) = @_;
    bless { @list }, $pkg;
}

sub FETCH {
    my ($tied,$key) = @_;
    if (!defined($tied->{$key})) {
        warn "$key is undefined!";
    }
    $tied->{$key};
}

sub STORE {
    my ($tied,$key,$val) = @_;
    $tied->{$key} = $val;
}

package Example;

sub new {
    my ($pkg,@list) = @_;
    my $self = {};
    tie %$self, 'Example::Tie', @list;
    bless $self, $pkg;
}

###########

package main;
my $exp = Example->new();
print $exp->{fieldname};

输出：

fieldname is undefined! at 45357987.pl line 10.

Perl - 在类中捕获未定义的键？

1 个答案: