Question

我有一个在for循环之外定义的哈希变量说

my %sports = (); #hash variable defined
my $count = 0; #key for the hash variable which will be used to populate the hash

在for循环中，我通过一些逻辑说明

填充了这个变量

$sports{$count} = "cricket"
$count++;

现在当我尝试在循环外打印映射到此哈希变量的所有值时，我收到错误

我进入了

print $count." -->  ".$sports{$count}  ;

我收到错误

在连接（。）或中使用％sports中的未初始化值
的字符串

Answer 1

而不是，

$sports{$count} = "cricket"
$count++;

尝试

$count++;
$sports{$count} = "cricket"

因此，$count将保留%sports哈希的最后一次使用密钥。

Answer 2

在最后一次分配后，您增加了$ count的值。因此，％sports散列中不存在新值。使用

print $count - 1, ' -->  ', $sports{ $count - 1 };

此外，如果您使用一系列数字作为哈希键，则可以切换到数组。

Answer 3

要打印映射到散列的所有值，请遍历键：

for my $count (keys %sports) {
    print $count." -->  ".$sports{$count};
}

Answer 4

错误是因为您正在尝试访问未分配的哈希值。

您的迭代就像这样

$count = 0

# Lets say loop goes from 0 to 5.
# So, when $count = 5 
    $sports{$count} = "cricket"
    $count++;  # Here $count becomes 6 and loop ends

print $sports{$count}  # Outside loop, Here $count is still 6, you are
                       # trying to print $sports{6}, which is unassigned

您需要先移动$count++

$count++;
$sports{$count} = "cricket"

在for循环中赋值后访问时哈希变量出错

4 个答案: