Method: Hash#inverse

Defined in:

lib/core/facets/hash/inverse.rb

#inverse ⇒ Object

Create a “true” inverse hash by storing mutliple values in Arrays.

h = {"a"=>3, "b"=>3, "c"=>3, "d"=>2, "e"=>9, "f"=>3, "g"=>9}

h.invert           #=> {2=>"d", 3=>"f", 9=>"g"}
h.inverse          #=> {2=>"d", 3=>["f", "c", "b", "a"], 9=>["g", "e"]}
h.inverse.inverse  #=> {"a"=>3, "b"=>3, "c"=>3, "d"=>2, "e"=>9, "f"=>3, "g"=>9}

Of course the inverse of the inverse should be the same.

(h.inverse.inverse == h)  #=> true

CREDIT: Tilo Sloboda

[View on GitHub]

# File 'lib/core/facets/hash/inverse.rb', line 17

def inverse
  i = Hash.new
  self.each_pair{ |k,v|
    if (Array === v)
      v.each{ |x| i[x] = ( i.has_key?(x) ? [k,i[x]].flatten : k ) }
    else
      i[v] = ( i.has_key?(v) ? [k,i[v]].flatten : k )
    end
  }
  return i
end