为什么我的Perl有福的文件句柄不能用`can（'print'）``返回true？ [英] Why doesn't my Perl blessed filehandle doesn't return true with `can('print')`'?

问题描述

出于某种原因，我无法使用Expect.pm的 log_file 方法获得文件句柄。我最初得到了如何将文件句柄传递给Perl Expect的log_file函数？，其中建议我使用一个IO :: Handle文件句柄传递给方法。这似乎是一个不同的问题，所以我想我会开始一个新的问题。

For some reason, I can't get filehandles working with Expect.pm's log_file method. I originally got help on How can I pass a filehandle to Perl Expect's log_file function?, where it was suggested that I use an IO::Handle filehandle to pass to the method. This seems to be a different issue, so I thought I'd start a new question.

这是Expect.pm的违规部分：

This is the offending section of Expect.pm:

if (ref($file) ne 'CODE') {
  croak "Given logfile doesn't have a 'print' method"
    if not $fh->can("print");
  $fh->autoflush(1);        # so logfile is up to date
}

那么，我试过这个示例代码：

So, then, I tried this sample code:

use IO::Handle;
open $fh, ">>", "file.out" or die "Can't open file";
$fh->print("Hello, world");
if ($fh->can("print"))
{
  print "Yes\n";
}
else
{
  print "No\n";
}

当我运行这个时，我得到两个（在我看来）冲突的项目。一个单行文件，说'你好，世界'和'不'的输出。在我看来， $ fh-> can 行应该返回true。我错了吗？

When I run this, I get two (to my mind) conflicting items. A file with a single line that says 'Hello, world', and output of 'No'. To my mind, the $fh->can line should return true. Am I wrong here?

推荐答案

奇怪的是，您需要创建一个真正的 IO :: File 对象获取可以方法工作。尝试

Odd, it looks like you need to create a real IO::File object to get the can method to work. Try

use IO::File;

my $fh = IO::File->new("file.out", ">>")
    or die "Couldn't open file: $!";

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