Ruby: What is the easiest method to update Hash values?
Solution 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.
Solution 2
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"}}
Solution 3
This will do:
h.each {|k, v| h[k] = foo(v)}
Solution 4
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.
Misha Moroshko
I build products that make humans happier. Previously Front End engineer at Facebook. Now, reimagining live experiences at https://muso.live
Updated on July 09, 2022Comments
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Misha Moroshko almost 2 years
Say:
h = { 1 => 10, 2 => 20, 5 => 70, 8 => 90, 4 => 34 }
I would like to change each value
v
tofoo(v
), such thath
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 ?