CODEWITHSUNDEEP
ruby
doremi
doremi

Reputation: 15329

Select Hash Value when Key is an Array

I have a hash that has some keys as an array like so:

foo = {[45, 121]=>:some_field}

How can I select :some_field where a foo key contains 45?

And secondary to that, if it finds a match, how do I retrieve the other elements in the same key?

Upvotes: 0

Views: 172

Answers (3)

Victor Moroz
Victor Moroz

Reputation: 9225

I would suggest to reverse your hash if it's not one element only:

foo = {[45, 121]=>:some_field, [1, 45, 7] => :some_other_field}

bar = {}
foo.each do |k, v|
  k.each do |x|
    if bar.has_key?(x)
      bar[x] << [[k, v]]
    else
      bar[x] = [[k, v]]
    end
  end
end

p bar[45]

Upvotes: 1

tadman
tadman

Reputation: 211600

Although you can do this, it kind of defeats the purpose of using a hash since you will have to do a linear scan through the entire thing. It would be a lot better to have multiple hash keys for the same value since you can use the hash as an index then.

Example:

found = foo.find { |k, v| k.include?(n) }
found and found[1]

Keep in mind the performance of this will be terrible if you have large numbers of entries in the key and a large number of items in the hash since it will have to test against all keys and all values individually.

Upvotes: 4

fl00r
fl00r

Reputation: 83680

foo = {[45, 121]=>:some_field}
foo.detect{ |k,v| k.include? 45 }
#=> [[45, 121], :some_field]
foo.detect{ |k,v| k.include? 45 }.last
#=> :some_field

Upvotes: 2

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