问题
I have just picked up Perl. I have a little confusion with accessing hash values. Below is the code where I am trying to access the values of a hash inside a hash. Since am using a simple text editor to code, I am not able to figure out what can be the problem. Please help
my %box = (
Milk => {
A => 5,
B => 10,
C => 20,
},
Chocolate => {
AB => 10,
BC => 25,
CD => 40,
},
);
foreach my $box_key(keys %box) {
foreach my $inside_key (keys %box{box_key})
print "$box_key"."_$inside_key""is for rupees $box{box_key}{inside_key}";
}
回答1:
ikegami has explained it very well and I feel that you are still missing something in your code that's why you are having a problem, try the below code, hope it helps you.
my %box = (
Milk => {
A => 5,
B => 10,
C => 20,
},
Chocolate => {
AB => 10,
BC => 25,
CD => 40,
},
);
foreach my $box_key(keys %box) {
foreach my $inside_key (keys $box{$box_key}) {
print "${box_key}_$inside_key is for rupees $box{$box_key}{$inside_key}\n";
}
}
Output:
Chocolate_CD is for rupees 40
Chocolate_BC is for rupees 25
Chocolate_AB is for rupees 10
Milk_A is for rupees 5
Milk_C is for rupees 20
Milk_B is for rupees 10
回答2:
If the syntax is
keys %hash
for a hash, it's
keys %{ ... }
for a hash reference. In this case, the reference is stored in $box{$box_key}
, so you'd use
keys %{ $box{$box_key} }
Also, you're accessing elements named box_key
and inside_key
in a couple of places where you actually want the elements named by $box_key
and $inside_key
.
Finally, you can use curlies around variable names to instruct Perl where the variable name ends.
for my $box_key (keys %box) {
for my $inside_key (keys %{ $box{$box_key} }) {
print "${box_key}_$inside_key is for rupees $box{$box_key}{$inside_key}\n";
}
}
来源:https://stackoverflow.com/questions/17036955/perlaccess-values-of-hash-inside-a-hash