From: "jeremyevans0 (Jeremy Evans)" <noreply@...>
Date: 2021-10-06T19:41:27+00:00
Subject: [ruby-core:105578] [Ruby master Feature#6669] A method like Hash#map but returns hash

Issue #6669 has been updated by jeremyevans0 (Jeremy Evans).

Status changed from Feedback to Closed

This was implemented by `Hash#to_h` taking a block starting in Ruby 2.6.

----------------------------------------
Feature #6669: A method like Hash#map but returns hash
https://bugs.ruby-lang.org/issues/6669#change-94037

* Author: yhara (Yutaka HARA)
* Status: Closed
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
----------------------------------------
Given a hash `h`, `h.map` returns an array(alist), but sometimes I hope it returned a hash.

Example:

~~~ruby
class Hash
  def apply(&block)
    self.inject({}) do |h, (k, v)|
      new_k, new_v = *block.call(k, v)
      h[new_k] = new_v
      h
    end
  end
end

score = {
  taro: [1,3,2],
  jiro: [3,5,8,4],
  saburo: [2,9]
}
max_score = score.apply{|k,v| [k, v.max]}
#=> {taro: 3, jiro: 8, saburo: 9}
p max_score[:taro]
#=> 3
~~~

I'm not thinking "`apply`" is a perfect name for this. Maybe "`hash_map`" is better
(we already have "`flat_map`").


---Files--------------------------------
6669.pdf (41.7 KB)


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