ruby, converting an array of hashes to a hash based on hash key

gistfile1.rb

def hasharray2hash(array, hash_key)
  if (!array.kind_of?(Array) || !hash_key.kind_of?(String)) 
    raise 'invalid parameters'
  end
  array.reduce({}){|cumulate,entry| 
    if !entry.kind_of?(Hash) 
      raise 'expecting a hash: ' + entry.to_s
    end

    key = entry[hash_key]
    if key == nil
      raise 'the entry ' + entry.to_s + " has not the required key " + hash_key
    end
    value = Hash[entry.select{|k,v| k != hash_key}]
    cumulate[key] = value
    cumulate
  }
end

servers = [
  { "name" => "server1", "address" => "10.10.10.11", "port" => 8080}, 
  { "name" => "server2", "address" => "10.10.10.12"}
]

hasharray2hash(servers, 'name')
# => {"server1"=>{"address"=>"10.10.10.11", "port"=>8080}, "server2"=>{"address"=>"10.10.10.12"}}

hasharray2hash(servers, 'address')
# => {"10.10.10.11"=>{"name"=>"server1", "port"=>8080}, "10.10.10.12"=>{"name"=>"server2"}}

hasharray2hash(servers, 'port')
# RuntimeError: the entry {"name"=>"server2", "address"=>"10.10.10.12"} has not the required key port