Issue #6669 has been updated by trans (Thomas Sawyer).


It would introduce an incompatibility, but probably not as much as you might think since #map has become the more commonly used method and it is used even less frequently on a Hash.

I think it makes good sense to have a known set of methods that are *closed*, which is to say they return the same class of object. As matz points out, #select and #reject are already closed. #collect could be made closed without too much trouble since we still have the more widely used #map.

That doesn't get rid of the need for a better Array to Hash conversion method though, which has been discussed in other threads.


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Feature #6669: A method like Hash#map but returns hash
https://bugs.ruby-lang.org/issues/6669#change-28275

Author: yhara (Yutaka HARA)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: 2.0.0


=begin
Given a hash h, h.map returns an array(alist), but sometimes I hope it returned a hash.

Example:

  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").
=end



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