From: naruse@...
Date: 2019-01-10T08:16:08+00:00
Subject: [ruby-dev:50758] [Ruby trunk Feature#6118][Feedback] Hash#keys_of(values), returns related keys of given values

Issue #6118 has been updated by naruse (Yui NARUSE).

Status changed from Assigned to Feedback

I forgot use case.

use case is welcome

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Feature #6118: Hash#keys_of(values), returns related keys of given values
https://bugs.ruby-lang.org/issues/6118#change-76194

* Author: naruse (Yui NARUSE)
* Status: Feedback
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 
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Hash#key(value) の複数版がほしいです。

{a: 1, b: 2, c: 3, d: 1}.key(1)
=> :a
というメソッドはあるのですが、
{a: 1, b: 2, c: 3, d: 1}.keys_of(1)
=> [:a, :d]
というメソッドは現状ありません。

Ruby での実装例は以下のような感じになります。
どうでしょうか。

class Hash
  def keys_of(*a)
    each_with_object([]) {|(k, v), r| r << k if a.include? v}
  end
end

---Files--------------------------------
000_ruby_hash_keys_of.patch (2.36 KB)
000_ruby_hash_keys_of.patch (2.36 KB)


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