CODEWITHSUNDEEP
rubyhashruby-1.9
Steve
Steve

Reputation: 2854

Check that a hash includes another hash

Given that I have an array of hashes abc and a hash ghi:

abc = [{
  'a' => '1',
  'b' => '2',
  'c' => '3',
  'd' => '4'
}]
ghi = {
  'a' => '1',
  'b' => '2'
}

what is the cleanest and most efficient way of selecting hashes from abc that contain all of the key-value pairs in ghi?

I was able to do this:

abc.map {|n| n.slice(*ghi.keys) == ghi }.all?

although it doesn't look very clean.

Upvotes: 2

Views: 1498

Answers (4)

Vasu Adari
Vasu Adari

Reputation: 908

abc.select{|h| ghi.all?{|k,v| h.key?(k) && h.value?(v) } }

Benchmark result:

require 'benchmark'
Benchmark.bm do |x|
  x.report { 10000.times { abc.select{|h| ghi.all?{|k,v| h.key?(k) && h.value?(v) } } } }
  x.report { 10000.times { abc.select{|h| h.merge(ghi) == h } } }
  x.report { 10000.times { abc.select{|hash| (ghi.to_a - hash.to_a).empty? } } }
  x.report { 10000.times { abc.select{|hash| (hash.values <=> ghi.values) == (hash.keys <=> ghi.keys) } } }
end

       user     system      total        real
   0.040000   0.000000   0.040000 (  0.037253)
   0.040000   0.000000   0.040000 (  0.046138)
   0.150000   0.000000   0.150000 (  0.155893)
   0.020000   0.000000   0.020000 (  0.028176)

Looks like Rajarshi's answer is the most efficient among all the answers.

Upvotes: 0

Rajarshi Das
Rajarshi Das

Reputation: 12330

For all keys and values check, you can try:

abc = [
  {
    'a' => '1',
    'b' => '2',
    'c' => '3',
    'd' => '4'
  },
  {
    'a' => '33',
    'b' => '23'
  }
]
d = {
  'a' => '1',
  'b' => '2'
}
abc.select{|hash| ((hash.values <=> d.values) == 1 ) && ((hash.keys <=> d.keys) == 1 )}
# => [{"a"=>"1", "b"=>"2", "c"=>"3", "d"=>"4"}]

Upvotes: 0

sawa
sawa

Reputation: 168131

In Ruby 2.3.

abc.select{|h| h >= ghi}

Note: This was answered before the OP mentioned the Ruby version.

Prior versions of Ruby:

abc.select{|h| h.merge(ghi) == h}

Upvotes: 8

Jay-Ar Polidario
Jay-Ar Polidario

Reputation: 6603

Not sure if this is the fastest.

abc.select{|hash| (ghi.to_a - hash.to_a).empty?}

Upvotes: 2

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