Feature #11818: `Hash#compact`

• Status: Closed
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -

[sawa (Tsuyoshi Sawada)]

I request Hash#compact and Hash#compact! that remove the key-value pairs whose value is nil, as follows:

h1 = {a:, 1, b: nil, c: 2}
h1.compact # => {a: 1, c: 2}
h1 # => {a: 1, b: nil, c: 2}

h2 = {a:, 1, b: nil, c: 2}
h2.compact! # => {a: 1, c: 2}
h2 # => {a: 1, c: 2}

h3 = {a:, 1, c: 2}
h3.compact! # => nil
h3 # => {a: 1, c: 2}

I believe people have frequent need to do this.

[sawa (Tsuyoshi Sawada)]

Sorry, the code was invalid. It should be:

h1 = {a: 1, b: nil, c: 2}
h1.compact # => {a: 1, c: 2}
h1 # => {a: 1, b: nil, c: 2}

h2 = {a: 1, b: nil, c: 2}
h2.compact! # => {a: 1, c: 2}
h2 # => {a: 1, c: 2}

h3 = {a: 1, c: 2}
h3.compact! # => nil
h3 # => {a: 1, c: 2}

[danielpclark (Daniel P. Clark)]

You can do this with Hash#delete_if

{a: 1, b: nil, c: 2}.delete_if {|k,v| v.nil?}
# => {:a=>1, :c=>2}

[sikachu (Prem Sichanugrist)]

Active Support has this: http://api.rubyonrails.org/classes/Hash.html#method-i-compact

I'm +1 on porting this method. While I think it's possible using a block form and delete_if, this method has a good name and intention that could live by its own.

[dwfait (Dwain Faithfull)]

Prem Sichanugrist wrote:

Active Support has this: http://api.rubyonrails.org/classes/Hash.html#method-i-compact

I'm +1 on porting this method. While I think it's possible using a block form and delete_if, this method has a good name and intention that could live by its own.

https://github.com/ruby/ruby/pull/1184/files

In anticipation of this being approved, I have raised a PR of a sample implementation, along with some benchmarks against the Active Support implementation and tests.

This is my first time contributing to Ruby, so I apologise if I've jumped the gun or done anything wrong - seemed like a good issue to pick up for someone new to the codebase, with no possible breaking changes, and some good performance gains to be had.

[mrkn (Kenta Murata)]

• Status changed from Open to Assigned
• Assignee set to matz (Yukihiro Matsumoto)

[matz (Yukihiro Matsumoto)]

Accepted.

Matz.

[nobu (Nobuyoshi Nakada)]

• Status changed from Assigned to Closed

Applied in changeset r56414.

---

hash.c: add compact and compact! methods

• hash.c (rb_hash_compact, rb_hash_compact_bang): Removes nil
  values from the original hash, to port Active Support behavior.
  [Feature #11818]