Method: DataTools::ArrayOfHashes#key_on

Defined in:
lib/data_tools/array_of_hashes.rb

#key_on(*keyarray) ⇒ Object

convert an array of hashes to a hash of the same hashes where the key values are picked from the hashes the keys can be single fields, or an array, or a list options:

:multi (boolean, default false): if true, allow multiple values per key; store values as an array for each key
:first (boolean, default false): if true, when finding multiple values per key, store only the first and ignore the rest
:truncate (integer): see `Hash#key_for`



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# File 'lib/data_tools/array_of_hashes.rb', line 10

def key_on(*keyarray)
  raise "Key(s) required" if keyarray.empty?
  opts = keyarray.last.is_a?(Hash) ? keyarray.pop : {}
  keyarray = keyarray.flatten

  memo = opts[:multi] ? Hash.new {|h,k| h[k] = []} : Hash.new
  each do |hash|
    this_key = hash.key_for(keyarray, opts)
    raise "Missing value for #{keyarray} in record #{hash}" if this_key.nil?
    if opts[:multi]
      memo[this_key] << hash
    elsif opts[:first]
      # ignore this value if we already have one for this key
      if !memo.has_key?(this_key)
        memo[this_key] = hash
      end
    else
      raise "Found duplicate #{keyarray} in #{memo[this_key]} vs #{hash}" if memo.has_key?(this_key)
      memo[this_key] = hash
    end
    memo
  end
  memo.extend DataTools::HashOfArrays
  memo.default = nil
  memo
end