[英]How to access an element in a Perl array from a reference to an array of references
I have the following Perl code: 我有以下Perl代码:
package CustomerCredit;
#!/usr/local/bin/perl
use 5.010;
use strict;
my $TransRef = @_; # This code comes from a sub within the package.
my ($Loop, $TransArrRef, $TransID);
for ($Loop = 0; $Loop < $$#TransRef; $Loop++)
{
$TransArrRef = $$TransRef[$Loop]; # Gets a ref to an array.
$TransID = $$TransArrRef[0]; # Try to get the first value in the array.
# The above line generates a compile time syntax error.
...
}
$TransRef is a reference to an array of references to arrays. $ TransRef是对数组引用数组的引用。 I am trying to process each element in the array pointed to by $TransRef. 我正在尝试处理$ TransRef指向的数组中的每个元素。 $TransArrRef should obtain a reference to an array. $ TransArrRef应获取对数组的引用。 I want to assign the first value within that array to $TransID. 我想将该数组中的第一个值分配给$ TransID。 But, this statement generates a compile syntax error. 但是,此语句会生成编译语法错误。
I must be doing something wrong, but can not figure out what it is. 我必须做错事,但无法弄清楚它是什么。 Can anyone help? 有人可以帮忙吗?
The syntax error is coming from $$#TransRef
which should be $#$TransRef
. 语法错误来自$$#TransRef
,它应该是$#$TransRef
。 By misplacing the #
you accidentally commented out the rest of the line leaving: 通过错放#
你意外地评论了剩余的线路离开:
for ($Loop = 0; $Loop <= $$
{
$TransArrRef = $$TransRef[$Loop];
...
}
$$
is ok under strict
as it gives you the process id leaving the compiler to fail further down. $$
是strict
因为它为您提供进程ID,让编译器进一步失败。
Also, $#$TransRef
gives you the last element in the array so you'd need <=
rather than just <
. 此外, $#$TransRef
为您提供数组中的最后一个元素,因此您需要<=
而不是<
。 Or use this Perl style loop: 或者使用这个Perl样式循环:
for my $loop (0 .. $#$TransRef) {
$TransID = $TransRef->[$loop]->[0];
# ...
}
my $arrays_ref = [ [1,2], [3,4] ];
for my $array_ref (@$arrays_ref) {
printf "%s\n", $array_ref->[0];
}
You can use foreach
as well: 你也可以使用foreach
:
my @array = ('val1', 'val2', 'val3') ;
my $array_ref = \@array ;
print "array size is $#{$array_ref} \n" ;
foreach $elem (@$array_ref) {
print "$elem \n"
}
Outputs: 输出:
array size is 2
val1
val2
val3
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