Recursive Hash#fetch

Posted by Ernie on March 11, 2008 at 2:37 pm

Recently, I found myself wishing for a recursive version of Hash#fetch that would get all values from a nested hash structure. I looked around for a while, and couldn’t find one, so I made a little mixin called Hash#fetch_all. It returns an array containing all values matching a given key from any level within such a structure. It definitely still feels like it could be improved on, but it works.



class Hash
  def fetch_all(key)
    results = []
    hashfinder = lambda {|h|
      arrayfinder = lambda {|a|
        a.each do |v|
          hashfinder[v] if v.is_a?(Hash)
          arrayfinder[v] if v.is_a?(Array)
        end
      }
      if h.has_key?(key)
        results << h.fetch(key)
      end
      h.values.each do |v|
        hashfinder[v] if v.is_a?(Hash)
        arrayfinder[v] if v.is_a?(Array)
      end
    }
    hashfinder.call(self)
    results
  end
end

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Tagged as coding, rails

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Recursive Hash#fetch

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