CODEWITHSUNDEEP
rubyhash
Misha Moroshko
Misha Moroshko

Reputation: 171489

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

Say:

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

I would like to change each value v to foo(v), such that h will be:

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

What is the most elegant way to achieve this ?

Upvotes: 55

Views: 86136

Answers (5)

MaximusDominus
MaximusDominus

Reputation: 2107

Rails (and Ruby 2.4+ natively) have Hash#transform_values, so you can now do {a:1, b:2, c:3}.transform_values{|v| foo(v)}

https://ruby-doc.org/core-2.4.0/Hash.html#method-i-transform_values

If you need it to work in nested hashes as well, Rails now has deep_transform_values(source):

hash = { person: { name: 'Rob', age: '28' } }

hash.deep_transform_values{ |value| value.to_s.upcase }
# => {person: {name: "ROB", age: "28"}}

Upvotes: 27

Gareve
Gareve

Reputation: 3391

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.

Upvotes: 119

rubyprince
rubyprince

Reputation: 17803

This will do:

h.each {|k, v| h[k] = foo(v)}

Upvotes: 12

Andrew Grimm
Andrew Grimm

Reputation: 81671

The following is slightly faster than @Dan Cheail's for large hashes, and is slightly more functional-programming style:

new_hash = Hash[old_hash.map {|key, value| key, foo(value)}]

Hash#map creates an array of key value pairs, and Hash.[] converts the array of pairs into a hash.

Upvotes: 6

dnch
dnch

Reputation: 9605

There's a couple of ways to do it; the most straight-forward way would be to use Hash#each to update a new hash:

new_hash = {}
old_hash.each do |key, value|
  new_hash[key] = foo(value)
end

Upvotes: 0

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