Question

I have a problem to solve, There is a simple supermarket program where all items are sorted and stored in a hash(key: Product ID) that has values such as price, manufacturer, expiry etc.
For a purpose, i need to group items according to price.
I need to create a hash (keyed: price) containing another hash (keyed: Product ID).

Code goes like this:

new_Hash = Hash.new(Hash.new)
items = Hash.new
SuperMarket_hash.each { |Product_ID, info | new_Hash[info.PRICE].items[Product_ID] }

I am getting error for this code. (items : NillClass no method error)

Answer 1

Use a vivified hash as shown in “Dynamically creating a multi-dimensional hash in Ruby“

Or use group_by.