Ruby creating Hash custom invert function in Ruby

Question

Ruby class Hash has method "invert" which make "reversal" between keys and values and delete same keys (in our case its: "1=>:a"). h = {a: 1, b: 2, c: 1} => {:a=>1, :b=>2, :c=>1} h.invert => {1=>:c, 2=>:b}

How implement custom Hash method "c_invert", which will return very first (not last) pair of duplicated key => value? Exapmle:

> h = {a: 1, b: 2, c: 1} 
=> {:a=>1, :b=>2, :c=>1} 
> h.c_invert 
=> {1=>:a, 2=>:b}

sawa · Accepted Answer · 2013-07-20 16:51:36Z

3

class Hash
  def c_invert
    Hash[to_a.reverse].invert
  end
end

or

class Hash
  def c_invert
    Hash[to_a.reverse.map(&:reverse)]
  end
end

answered Jul 20, 2013 at 16:51

sawa

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Comments

Arup Rakshit · Accepted Answer · 2013-07-20 23:11:23Z

0

h =  {:d =>1,:a=>1, :b=> 2, :c=>1}
Hash[h.map(&:reverse).reverse]
# => {1=>:d, 2=>:b}

h = {a: 1, b: 2, c: 1} 
Hash[h.map(&:reverse).reverse]
# => {1=>:a, 2=>:b}

edited Jul 20, 2013 at 23:11

answered Jul 20, 2013 at 17:00

Arup Rakshit

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