Perl的：
如何使用 JSON :: PP对复杂结构进行排序？
如何使用 JSON :: PP对复杂结构进行排序？
从JSON文档：
As the sorting routine runs in the
JSON::PP scope,the given subroutine
name and the special variables $a,$b
will begin ‘JSON::PP::’.
这是我的尝试,似乎没有用
open my $fh,">",$file or warn " exportAsJSON: can't open file: '$file': $!";
print $fh $coder->sort_by(sub {$_->{column_def}->{$JSON::PP::a} cmp $_->{column_def}->{$JSON::PP::b} } )->encode(\%json);
close $fh;
我想按键排序,然后在“column_def”下面的属性键上的column_def属性,即
密度,depth_in_m,mag_sus
：
{
"column_def":
{
"depth_in_m":
{
"names":"depth_in_m","pos":"0"
},"mag_sus":
{
"names":
{
"A_ALIAS":"Mag-Sus.","A_DESC":"magnetic susceptibility in SI","ATTRIBUTE":"MAG_SUS"
},"pos":"2"
},"density":
{
"names":
{
"A_ALIAS":"Density","A_DESC":"density in gm\/cc","ATTRIBUTE":"DENSITY"
},"pos":"1"
}
},"data":
{
"depth_in_m":"14.635","mag_sus":"n.a.","density":"n.a."
}
}
解决方法
我不确定我是否理解你希望如何排序JSON输出 – 除了按哈希键排序.如果这就是你想要的,只需将规范方法传递给真正的参数即可.
use strict;
use warnings;
use JSON::PP;
# A simple hash-of-hashes for exploration.
my $h = {
Z => { c => 1,d => 2 },A => { a => 3,r => 4 },B => { c => 5,x => 6 },S => { q => 7,d => 8 },};
my $js = JSON::PP->new;
$js->canonical(1);
my $output = $js->encode($h);
print $output;
如果你确实使用了sort_by方法,那么在sort块中使用$_是没有意义的：它代表什么？从文档中不清楚sort_by代码将接收哪些参数.像这样使用Data :: Dumper：
use Data::Dumper qw(Dumper);
my $sorter = sub {
# See what's going on.
print "$JSON::PP::a cmp $JSON::PP::b\n";
print Dumper(\@_,$_);
<STDIN>;
# Sort hash keys alphabetically.
$JSON::PP::a cmp $JSON::PP::b;
};
my $output = $js->sort_by($sorter)->encode($h);
你可以推断sort_by的工作原理如下：(1)它接收两个参数,即JSON :: PP对象和当前正在处理的散列引用; (2)$JSON :: PP :: a和$JSON :: PP :: b变量保存正在比较的散列键.但请注意,散列引用是指JSON输出,因为它是从叶节点向上构建的.它不涉及您的原始数据结构.这似乎使编写比较器的任务有点棘手.祝好运.
my $sorter = sub {
my ($json_pp_object,$hash_ref) = @_;
# Write your own comparator here.
};
my $output = $js->sort_by($sorter)->encode($h);