Project

General

Profile

Actions

Feature #12461

closed

Hash & keys to make subset.

Added by ioquatix (Samuel Williams) over 8 years ago. Updated over 8 years ago.

Status:
Rejected
Assignee:
-
Target version:
-
[ruby-core:75851]

Description

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.


Related issues 1 (0 open1 closed)

Related to Ruby master - Feature #8499: Importing Hash#slice, Hash#slice!, Hash#except, and Hash#except! from ActiveSupportClosedmatz (Yukihiro Matsumoto)Actions

Updated by ioquatix (Samuel Williams) over 8 years ago

Just to add to this, I also found an implementation here:

https://github.com/rubyworks/facets/blob/master/lib/core/facets/hash/slice.rb

Now I wonder if this warrants being in the standard library. I believe it probably does since it appears lots of people are using it, and it would probably be significantly faster written in C.

Actions #2

Updated by shyouhei (Shyouhei Urabe) over 8 years ago

  • Related to Feature #8499: Importing Hash#slice, Hash#slice!, Hash#except, and Hash#except! from ActiveSupport added

Updated by matz (Yukihiro Matsumoto) over 8 years ago

  • 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.

Updated by usa (Usaku NAKAMURA) over 8 years ago

  • Tracker changed from Bug to Feature
  • Status changed from Closed to Rejected
Actions

Also available in: Atom PDF

Like0
Like0Like0Like0Like0