ruby slice with array cirteria

Question

How can I create an slice for a hash in ruby looking by an array, like this:

info         = { :key1 => "Lorem", :key2 => "something...", :key3 => "Ipsum" }
needed_keys  = [:key1, :key3]
info         = info.slice( needed_keys )

I want to receive:

{ :key1 => "Lorem", :key3 => "Ipsum" }

score 5 · Accepted Answer · edited May 23 '17 at 11:57

5

ActiveSupport's Hash#slice doesn't take an array of keys as argument, you have to pass the keys you want to extract as single arguments, for example by splatting your needed_keys array:

info.slice(:key1, :key3)
# => {:key1=>"Lorem", :key3=>"Ipsum"}

info.slice(*needed_keys)
# => {:key1=>"Lorem", :key3=>"Ipsum"}

edited May 23 '17 at 11:57

Community

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answered Jan 14 '14 at 16:52

toro2k

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It might take an array, if someone is using arrays as a key. :) – BroiSatse Jan 14 '14 at 16:53
2

Hash#slice is from ActiveSupport, please include this in your answer – bjhaid Jan 14 '14 at 16:54

score 2 · Answer 2 · answered Jan 14 '14 at 16:51

2

info.select{|k,_| needed_keys.include? k }

answered Jan 14 '14 at 16:51

Santhosh

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Though less direct, another pure-Ruby way: `Hash[needed_keys.zip(info.values_at(*needed_keys))]`. – Cary Swoveland Jan 14 '14 at 19:32

score 1 · Answer 3 · answered Jan 14 '14 at 16:52

1

You need to expand array:

info.slice(*needed_keys)

answered Jan 14 '14 at 16:52

BroiSatse

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ruby slice with array cirteria

3 Answers3