Ruby 1.9.2 リファレンスマニュアル > ライブラリ一覧 > csvライブラリ > CSV::Tableクラス > each
each {|header, field| ... } -> self
In the default mixed mode or row mode, iteration is the standard row major walking of rows. In column mode, interation will +yield+ two element tuples containing the column name and an Array of values for that column.
This method returns the table for chaining.