为什么这个条件不起作用?带类的 Div [英] Why is this condition not working? Div with class

问题描述

我有一个条件，我想从特定标签中检索文本，但它似乎没有返回 true.. 有什么帮助吗?

I have a condition where i want to retrieve text from a specific tag, but it does not seem to be returning true.. any help?

#!/usr/bin/perl

use HTML::TreeBuilder;
use warnings;
use strict;
my $URL = "http://prospectus.ulster.ac.uk/modules/index/index/selCampus/JN/selProgramme/2132/hModuleCode/COM137";
my $tree = HTML::TreeBuilder->new_from_content($URL);  

if (my $div = $tree->look_down(_tag => "div ", class => "col col60 moduledetail")) {
 printf $div->as_text();
          print "test";
 open (FILE, '>mytest.txt');
 print FILE $div;
 close (FILE); 
}
      print $tree->look_down(_tag => "th", class => "moduleCode")->as_text();
 $tree->delete();

它没有进入 if 语句，并且 if 语句外的打印表明有一个未定义的值，但我知道它应该返回 true，因为这些标签确实存在.

It is not getting into the if statement and the print outside the if statement is saying that there is an undefined value, but i know that it should be returning true because these tags do exist.

<th class="moduleCode">COM137<small>CRN: 33413</small></th>

谢谢

推荐答案

您正在调用 HTML::TreeBuilder->new_from_content 但您提供的是 URL 而不是内容.您必须先get HTML，然后才能将其传递给HTML::TreeBuilder.

You are calling HTML::TreeBuilder->new_from_content yet you are supplying a URL instead of content. You have to get the HTML before you can pass it to HTML::TreeBuilder.

也许最简单的方法是使用 LWP::Simple 导入一个名为获取.这将读取 URL 中的数据并将其作为字符串返回.

Perhaps the simplest way is to use LWP::Simple which imports a subroutine called get. This will read the data at the URL and return it as a string.

您的条件块从未执行的原因是您的标签名称中有一个空格.您需要 "div" 而不是 "div".

The reason your conditional block is never executed is that you have a space in the tag name. You need "div" instead of "div ".

还要注意以下几点:

• 您不应该使用 printf 将该字符串作为格式说明符来输出单个字符串.它可能会生成缺少参数警告并且无法正确输出字符串.

• You shouldn't output a single string by using printf with that string as a format specifier. It may generate missing argument warnings and fail to output the string properly.

理想情况下，您应该使用词法文件句柄和 open 的三参数形式.您还应该检查所有 open 调用的状态并做出相应的响应.

You should ideally use lexical file handles and the three-argument form of open. You should also check the status of all open calls and respond accordingly.

你的标量变量 $div 是一个有福的哈希引用，所以按原样打印它会输出类似 HTML::Element=HASH(0xfffffff).你需要调用它的方法来提取你想要显示的值

Your scalar variable $div is a blessed hash reference, so printing it as it is will output something like HTML::Element=HASH(0xfffffff). You need to call its methods to extract the values you want to display

纠正这些错误后，您的代码看起来像这样，尽管我没有格式化输出，因为我不知道您想要什么.

With these errors corrected your code looks like this, although I haven't formatted the output as I can't tell what you want.

use strict;
use warnings;

use HTML::TreeBuilder;
use LWP::Simple;

my $url = "http://prospectus.ulster.ac.uk/modules/index/index/selCampus/JN/selProgramme/2132/hModuleCode/COM137";
my $html = get $url;
my $tree = HTML::TreeBuilder->new_from_content($html);  

if (my $div = $tree->look_down(_tag => "div", class => "col col60 moduledetail")) {
  print $div->as_text(), "\n";
  open my $fh, '>', 'mytest.txt' or die "Unable to open output file: $!";
  print $fh $div->as_text, "\n";
}

print $tree->look_down(_tag => "th", class => "moduleCode")->as_text, "\n";

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