[ruby-core:76423] [Ruby trunk Bug#12461][Closed] Hash & keys to make subset.

Issue #12461 has been updated by Yukihiro Matsumoto.

Status changed from Open to Closed

I am against having `Hash#&`. `Array#&` takes two arrays. The proposed `Hash#&` takes a hash and key array.
if you want `Hash#slice` to be added to the core, submit a new issue. But note that now we have real
keyword arguments so that we have less need for manipulating keyword hashes explicitly. 

Matz.


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Bug #12461: Hash & keys to make subset.
https://bugs.ruby-lang.org/issues/12461#change-59666

* Author: Samuel Williams
* Status: Closed
* Priority: Normal
* Assignee: 
* ruby -v: 
* Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
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It would be nice if Hash had a way to create a sub-hash with a limited set of keys. This would be useful for keyword functions in particular, because sometimes you have a large hash of things and you only want to send a subset to another function.

A definition somewhat like:

    class Hash
        def &(keys)
            keys.each_with_object(self.class.new) {|key, hash| hash[key] = self[key] if has_key?(key)}
        end
    end

You can see some similar definitions here: https://github.com/rails/rails/blob/b670fadb978c8a12c3414ed842cd49e4fde2cec0/activesupport/lib/active_support/core_ext/hash/slice.rb#L21

It might be nice to support `slice` and `slice!` in a similar logical sense to `Array` rather than proposed `&` operator above - that would just be nice shortcut.



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