change value in hash using an array of keys in ruby

Question

i was wondering if it is possible to access an value of a hash with an array of keys as described in the post ruby use array tvalues to index nested hash of hash . My aim is not just to access this value but to change this value. As I understood

keys.inject(hash, :fetch)

returns the value of the hash-value determined by the key-array and not it's reference. How can I accomplish to modify this value?

I know it's bad style to modify an object instead of making a copy and working with immutables but in severel cases it seems much more comfortable to do it the short way.

Thanks a lot.

Answer 1

Use all but the last key to get the most deeply nested Hash, then assign normally using the last key.

keys[0...-1].inject(hash, :fetch)[keys.last] = value

Ruby doesn't have references so you can't reassign the value directly. Instead you have to reassign the object pointer, which means going up one level of nesting.