'perldoc -f每个'说我在迭代时不安全删除或添加值,除非该项目是每个()最近返回的()。
运行此代码snnipet时:
my ($key,$value);
my %fruits = qw/ banana 1 apple 2 grape 3 /;
while ( $key = each %fruits ) {
$fruits{$key} *= 7;
print "$key = $fruits{$key}n";
}
print "nRead onlynn";
while ( ($key,$value) = each %fruits ) {
print "$key = $valuen";
}
一切正常!
,但是如果我使用绑带的哈希,humnn:
#-------------------------------------------------------------------------------
# select entries on database to print or to update.
sub select_urls {
my ($dbPath,$match,$newValue) = @_;
tie(my %tiedHash,'DB_File',$dbPath,O_RDWR|O_EXLOCK,0600,$DB_BTREE) || die("$program_name: $dbPath: $!n");
while ( my($key,$value) = each %tiedHash ) {
if ( $key =~ $match ){
if ( defined $newValue ) {
$tiedHash{$key} = $newValue;
($key,$value) = each %tiedHash; # because 'each' come back 1 step when we update the entry
print "Value changed --> $key = $valuen";
} else {
print "$key = $valuen";
}
}
}
untie(%tiedHash) || die("$program_name: $dbPath: $!n");
}
是对每个()的第二个调用。
我必须'perl -v':
$ perl -v
这是perl 5,版本12,颠覆2(v5.12.2(*)) AMD64 -OPENBSD(带有8个注册的补丁,请参见Perl -V,有关更多详细信息)
版权1987-2010,拉里·沃尔 ...
我在想这是错误吗?!!
也许更多的东西在幕后...
我问我的解决方案是否正确?
这是问题的添加或去除元素(键)。应该没有更改价值的问题。与绑定的哈希没有固有的区别。
my ($key,$value);
use Tie::Hash;
tie my %fruits, 'Tie::StdHash';
%fruits = qw/ banana 1 apple 2 grape 3 /;
while ( $key = each %fruits ) {
$fruits{$key} *= 7;
print "$key = $fruits{$key}n";
}
print "nRead onlynn";
while ( ($key,$value) = each %fruits ) {
print "$key = $valuen";
}
输出:
banana = 7
apple = 14
grape = 21
Read only
banana = 7
apple = 14
grape = 21
您的第二个片段没有演示错误。它并没有表现出太多。它无法运行,您没有指定输出的内容,也没有指定其期望输出的内容。但是,让我们看看db_file是否有问题。
use DB_File qw( $DB_BTREE );
use Fcntl qw( O_RDWR O_CREAT ); # I don't have O_EXLOCK
my ($key,$value);
tie(my %fruits, 'DB_File', '/tmp/fruits', O_RDWR|O_CREAT, 0600, $DB_BTREE)
or die $!;
%fruits = qw/ banana 1 apple 2 grape 3 /;
while ( $key = each %fruits ) {
$fruits{$key} *= 7;
print "$key = $fruits{$key}n";
}
print "nRead onlynn";
while ( ($key,$value) = each %fruits ) {
print "$key = $valuen";
}
nope。
apple = 14
banana = 7
grape = 21
Read only
apple = 14
banana = 7
grape = 21