这是从
AnyEvent::Intro摘录
# register a read watcher
my $read_watcher; $read_watcher = AnyEvent->io (
fh => $fh,poll => "r",cb => sub {
my $len = sysread $fh,$response,1024,length $response;
if ($len <= 0) {
# we are done,or an error occurred,lets ignore the latter
undef $read_watcher; # no longer interested
$cv->send ($response); # send results
}
},);
为什么使用
my $read_watcher; $read_watcher = AnyEvent->io (...
代替
my $read_watcher = AnyEvent->io (...
？
解决方法
因为闭包引用$read_watcher,并且$read_watcher解析为词法的范围只从包含我的语句开始.
这是有意的,所以这样的代码指的是两个单独的变量：
my $foo = 5;
{
my $foo = $foo;
$foo++;
print "$foo\n";
}
print "$foo\n";