[ruby-dev:50116] [Ruby trunk Feature#13563] Implement Hash#choice method.

Issue #13563 has been updated by matthewd (Matthew Draper).


FWIW, ActiveSupport calls this `Hash#slice` -- http://api.rubyonrails.org/classes/Hash.html#method-i-slice

(With one small behavioural difference: keys not present in the source hash are also omitted from the result, so the second example would return `{ "c" => true }`, not `{ "c" => true, 10000 => nil }`.)

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Feature #13563: Implement Hash#choice method.
https://bugs.ruby-lang.org/issues/13563#change-64810

* Author: babanba-n (matzbara masanao)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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Hi,

I propose Hash#choice method.

It pick up key and value pairs in Hash like a below code.

~~~
{ :a => 1, 2 => "2", "c" => true }.choice(:a, 2) # => { :a => 1, 2 => "2" }
{ :a => 1, 2 => "2", "c" => true }.choice("c", 10000) # => { "c" => true, 10000 => nil }
~~~

This method is useful when Hash have many keys, but programer need few key's.

For instance, it pick up personal data in ActiveRecord model's data, and migrate to new device.

~~~
feature_phone_user = User.find(params[:src_user_id])
profile = feature_phone_user.attributes.choice(*%i[nickname email sex birthday prefecture])
smart_phone_user   = User.new
smart_phone_user.attributes = profile
~~~
In other case, it pick up latest log from http request parameter.

~~~
condition = params.to_h.choice("user_id", "service_id")
latest_payment_log = PaymentLog.find_by(condition).last
~~~

If this method exist, I guess that many cases change to comfortable just a little.

Please consider about it.

And I write it.
https://github.com/baban/ruby/commit/4014ebe2ae261881669bef8369eb08aaecef2034




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