enumerable_transformer.rb

require 'coercible'

class Transformer
  include Enumerable

  COERCER = Coercible::Coercer.new

  COERCIONS = Hash.new(:to_string).update(
    id:         :to_integer,
    updated_on: :to_date,
    active:     :to_boolean,
  )

  def initialize(rows)
    @rows = rows
  end

  def each
    return to_enum unless block_given?
    @rows.each do |row|
      yield row.map { |key, value|
        COERCER[value.class].public_send(COERCIONS[key], value)
      }
    end
    self
  end
end

rows = [
  {
    id:         '1',
    name:       'Dan Kubb',
    updated_on: '2013-01-01',
    active:     'yes',
  }
]

Transformer.new(rows)

class Transformer
  IDENTITY = ->(value) { value }
  COERCER  = Coercible::Coercer.new

  COERCIONS = Hash.new(IDENTITY).update({
    'ga:date'      => ->(value) { Date.strptime(value, '%Y%m%d') },
    'ga:visitors'  => COERCER[String].method(:to_integer),
    'ga:visits'    => COERCER[String].method(:to_integer),
    'ga:newVisits' => COERCER[String].method(:to_integer),
  })

  # @param [Array] columns the array of column names
  # @param [Array] the rows of data
  def self.coerce(columns, rows)
    rows.map do |row|
      hash = columns.zip(row)
      hash.map do |key, value|
        COERCIONS[key][value]
      end
    end
  end
end