Ruby: What is the easiest method to update Hash values?

Question

Say:

h = { 1 => 10, 2 => 20, 5 => 70, 8 => 90, 4 => 34 }

I would like to change each value v to foo(v

Answer 1

You can use update (alias of merge!) to update each value using a block:

hash.update(hash) { |key, value| value * 2 }

Note that we're effectively merging hash with itself. This is needed because Ruby will call the block to resolve the merge for any keys that collide, setting the value with the return value of the block.