怎么判断hash中指定的结构是否存在？

lybpyn

回复 20# sosflyer

1. #!/usr/bin/perl -w
   
2. use XML::Simple;
   
3. use Data::Dumper;
   
4. use strict;
   
5. 
   
6. my $xml = new XML::Simple;
   
7. 
   
8. my $conf = $xml->XMLin("data.xml");
   
9. my $i=0;
   
10. my $j=0;
    
11. my $m=0;
    
12. my $d=0;
    
13. my @agr;
    
14. my @arr;
    
15. 
    
16. my $filename="";
    
17. my $filename2="";
    
18. my $value=0;
    
19. my $value2=0;
    
20.          while($conf->{'measData'}->{'measInfo'}->[$i])
    
21.        {
    
22.                          $filename=$conf->{'measData'}->{'measInfo'}->[$i]->{'measInfoId'};
    
23.                          my $tmp=$filename;
    
24.                          $filename.="-measTypes.txt";
    
25.                          open(fhn,">$filename")|| die $!;
    
26.                          
    
27.                          my $a=$conf->{'measData'}->{'measInfo'}->[$i]->{'measTypes'};
    
28.                          my @arg=split/\s+/,$a;
    
29.                          
    
30.                          while(@arg)
    
31.                    {
    
32.                      $value=shift(@arg);
    
33.                          $j ++;
    
34.              print fhn ("$j\t$value\n");
    
35.                    }
    
36.            close (fhn);
    
37.            
    
38.                    $filename2=$tmp."-measResults.txt";
    
39.            open(fhn2,">$filename2")|| die $!;
    
40.                    #$d=exists $conf->{'measData'}->{'measInfo'}->[$i]->{'measValue'}->[$m];
    
41.                    if ( exists $conf->{'measData'}->{'measInfo'}->[$i]->{'measValue'}->[$m])
    
42.                    {
    
43.                    my $c=$conf->{'measData'}->{'measInfo'}->[$i]->{'measValue'}->[$m];
    
44.                    while($conf->{'measData'}->{'measInfo'}->[$i]->{'measValue'}->[$m]->{'measResults'})
    
45.                    {
    
46.            my $b=$conf->{'measData'}->{'measInfo'}->[$i]->{'measValue'}->[$m]->{'measResults'};
    
47.                    my @arr=split/\s+/,$b;
    
48.                    while(@arr)
    
49.                    {
    
50.                            $value2=shift(@arr);
    
51.                            print fhn2 ("\t$value2\n");
    
52.                    }
    
53.                    $m ++;
    
54.                    }
    
55.                    }
    
56.                    else
    
57.                    {
    
58.                            while($conf->{'measData'}->{'measInfo'}->[$i]->{'measValue'}->{'measResults'})
    
59.                    {
    
60.            my $b=$conf->{'measData'}->{'measInfo'}->[$i]->{'measValue'}->{'measResults'};
    
61.                    my @arr=split/\s+/,$b;
    
62.                    while(@arr)
    
63.                    {
    
64.                            $value2=shift(@arr);
    
65.                            print fhn2 ("\t$value2\n");
    
66.                    }
    
67.                    }
    
68.                    }
    
69.                   
    
70.                    close (fhn2);
    
71.                    $i ++;
    
72.                    $j =0;
    
73.        }
    
74. 
    
75.    
    

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lybpyn

回复 20# sosflyer


    实际上用或者不用它都会提示报错 没区别

sosflyer

回复 22# lybpyn


    囧，好像你53行这个m++位置有问题

lybpyn

回复 23# sosflyer


    真不是哪的问题！就是因为没有找到所需结构才报错！m++位置没错他是要遍历xml中measValue节点下的所有值

Perlvim

散列的键，不能使用引用。

lybpyn

回复 25# Perlvim


    可以使用啊！怎么会不能用呢

jason680

7楼: 常用Data::Dumper看看吧

看了就知道了....别再浪费时间了....

lybpyn

回复 27# jason680


    我做xml解析需要判断一下 因为有些结构存在有些不存在  直接看结构没啥用

jason680

It's up to you

Perlvim

http://perldoc.perl.org/perlfaq4 ... ce-as-a-hash-key%3F

How can I use a reference as a hash key?

(contributed by brian d foy and Ben Morrow)

Hash keys are strings, so you can't really use a reference as the key. When you try to do that, perl turns the reference into its stringified form (for instance, HASH(0xDEADBEEF) ). From there you can't get back the reference from the stringified form, at least without doing some extra work on your own.

Remember that the entry in the hash will still be there even if the referenced variable goes out of scope, and that it is entirely possible for Perl to subsequently allocate a different variable at the same address. This will mean a new variable might accidentally be associated with the value for an old.

If you have Perl 5.10 or later, and you just want to store a value against the reference for lookup later, you can use the core Hash::Util::Fieldhash module. This will also handle renaming the keys if you use multiple threads (which causes all variables to be reallocated at new addresses, changing their stringification), and garbage-collecting the entries when the referenced variable goes out of scope.

If you actually need to be able to get a real reference back from each hash entry, you can use the Tie::RefHash module, which does the required work for you.