From: "marcandre (Marc-Andre Lafortune)" <ruby-core@...>
Date: 2013-09-01T04:05:04+09:00
Subject: [ruby-core:56946] [ruby-trunk - Feature #7292][Open] Enumerable#to_h


Issue #7292 has been updated by marcandre (Marc-Andre Lafortune).

Status changed from Feedback to Open
Priority changed from Low to Normal

matz (Yukihiro Matsumoto) wrote:
> What I wanted was coner case behavior of #to_h, e.g. what if elements are not 2 elements arrays.
> What kind of checks do you want to do?
> 
> The simplest implementation in #6 may work, but I'm not sure whether kind of accidental behavior definition is suffice.

I think it might be best to ignore anything that is not a key-value pair. So we should use an implementation slightly different from #6. In Ruby:

module Enumerable
  def to_h
    h = {}
    each_entry do |ary|
      next unless ary.respond_to?(:to_ary)
      ary = ary.to_ary
      raise TypeError unless ary.is_a?(Array)
      next unless ary.size == 2
      h[e.first] = e.last
    end
    h
  end
end


Note that I am using `each_entry`, so `yield(:key, :value)` is treated the same as `yield([:key, :value])`.
----------------------------------------
Feature #7292: Enumerable#to_h
https://bugs.ruby-lang.org/issues/7292#change-41505

Author: marcandre (Marc-Andre Lafortune)
Status: Open
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: next minor


Now that #to_h is the official method for explicit conversion to Hash, we should also add

	Enumerable#to_h: Returns a hash for the yielded key-value pairs.

	  [[:name, 'Joe Smith'], [:age, 42]].to_h # => {name: 'Joe Smith', age: 42}


With the Ruby tradition of succint documentation I suggest the documentation talk about key-value pairs and there is no need to be explicit about the uninteresting cases like:

    (1..3).to_h           # => {1 => nil, 2 => nil, 3 => nil}
    [[1, 2], [1, 3]].to_h # => {1 => 3}
    [[1, 2], []].to_h     # => {1 => 2, nil => nil}

I see some reactions of people reading about the upcoming 2.0 release like this one:
http://globaldev.co.uk/2012/11/ruby-2-0-0-preview-features/#dsq-comment-body-700242476



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