arrays - 为什么这会复制或覆盖列表的内容？

Question

我是 Perl 的新手，我不太明白我的代码有什么问题。我相信我正确使用了语法，但我怀疑问题可能出在这一行:

push @students, \%information;

我想要的是让学生列表包含学生信息的哈希值。我期望的是，每次添加学生后，都会创建学生信息的另一个哈希值，并链接到列表的最新索引。但是会发生什么，如果我同时输入学生数据，最新的会覆盖以前的，所以当你打印它时，你会在以前的列表条目中看到最新输入的信息的副本。如果我输入了1个学生并在添加后立即查看，然后输入另一个学生，最新的学生会覆盖之前的学生。有人可以阐明这一点吗？谢谢!

这是我的代码:

use strict;
use warnings;

my $userchoice = 0;
my $i;
my @students    = ();    #empty array
my %information = ();

while ( $userchoice != 4 ) {
    print "------------------------------\n";
    print "Welcome! What would you like to do?\n";
    print "[0]Create Student Record\n";
    print "[1]Edit Student Record\n";
    print "[2]View Student Record\n";
    print "[3]Delete Student Record\n";
    print "[4]Exit\n";
    print "Your Choice : ";
    $userchoice = <STDIN>;
    chomp($userchoice);

    if ( $userchoice == 0 ) {
        print "-----------\n";
        print "CREATE STUDENT RECORD.\n";
        if ( $#students <= 9 ) {
            print "Name : ";
            $information{"name"} = <STDIN>;
            chomp( $information{"name"} );
            push @students, \%information;
        }
        print "Student Record Full. " if ( $#students >= 10 );
    }

    if ( $userchoice == 2 ) {
        print "\nVIEW STUDENTS.\n";
        print "[0]View One Student\n";
        print "[1]View All Students\n";
        print "[2]Back to Main Menu\n";
        print "Your Choice : ";
        $userchoice = <STDIN>;
        if ( $userchoice == 1 ) {
            print "VIEW ALL STUDENTS.\n";

            print "STUDENT 1---------------\n";
            print "Name : ", $students[0]->{"name"}, " \n";
            print "STUDENT 2---------------\n";
            print "Name : ", $students[1]->{"name"}, " \n";
        }
    }
}

Answer 1

这总是将对同一散列的引用推送到数组 push @students,\%information;举例说明:

my %hash = ( index => 0 );
my @list = ();
foreach my $i (1..3) {
    $hash{index} = $i;
    push @list, \%hash;
}

for ( my $i=0; $i<@list; $i++ ) {
    print "item $i - $list[$i] - $list[$i]->{index}\n";
}

从输出中注意到每个地址都是相同的:

item 0 - HASH(0x4c8068) - 3
item 1 - HASH(0x4c8068) - 3
item 2 - HASH(0x4c8068) - 3

您可以通过在循环内声明 %information 来修复

while($userchoice!=4){
    my %information = ();

或者在推送时强制使用新的引用:

push @students, { %information };