Issue #13563 has been updated by babanba-n (matzbara masanao).


At first, I overlook Hash#slice method. Sorry... 
And, I reconsider about it. 

I feel that Hash#slice is wrong name and Hash#pick is better name. 
If key is not exist, key omit or return nil.
It is difficult problem. 

I think each way have usecase. 

For example, below code is return first row. 

``` 
Item = ItemStock.find_by({}) # return first row 
``` 

For that reason, below code may return unintended data. 

``` 
item = ItemStock.find_by(params.to_h.slice("user_id","item_id")) 
return render { result: "NG" } if item.amount.zero?
item.consume 
render json: { result: "OK" }
``` 

So returning nil is more safety.


----------------------------------------
Feature #13563: Implement Hash#choice method.
https://bugs.ruby-lang.org/issues/13563#change-64844

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