setting variable name with variable at the end - perl - perl

Question

$id = 1;
foreach (#products) {
$productid$id = param(product$id);
++$id;
}
I am trying to loop through the products array and create a new variable for each item in products for a form which uses checkboxes to select products which are for sale. I tried to use $productid$id and $productid"$id" but it returned syntax errors. Is there a way to achieve this?

Answer 1

I am trying to loop through the products array and create a new variable for each item in products.
While it is possible to create a new variable for each item, it's a bad idea. They have to be global, the syntax is ugly, and it's difficult to pass those variables around as a collection. Instead, use a hash or an array. In this case, since your items are indexed by number and there's no gaps an array makes the most sense.
my #product_params;
foreach my $product (#products) {
push #product_params, param($product);
}
For each $product in #products, it will add param($product) to #product_params. For example, the parameter for $products[5] is stored in $product_params[5].
Since this is a one-to-one mapping of #products to its parameters, its easier and faster to do the above with a map. A mapping runs each element of a list through a function to create a new list. $_ contains each element of #products in turn.
my #product_params = map { param($_) } #products;

Answer 2

Variables aren't interpolated in single quotes.
You're resetting the $id in each iteration of the loop.
Update: Your changes invalidated both the bullets above.
my $id = 1;
for my $product (#products) {
$product_id = param("product$id");
++$id;
}

Answer 3

Say you have four checkboxes named
product1
product2
product3
product4
Say product1 and product3 are checked.
The following will place 1 and 3 in #selected_product_ids:
my #selected_product_ids =
map { my ($id) = /^product(\d+)\z/; defined($id) && param($_) ? $id : () }
params();
If you have the list of all existing product ids in #product_ids, the following will do the same:
my #selected_product_ids =
grep { param("product$_") }
#product_ids;