instance method CSV::FieldInfo#header

利用可能な場合はヘッダを表す文字列を返します。

例

require 'csv'

csv = CSV.new("date1,date2\n2018-07-09,2018-07-10", headers: true)
csv.convert do |field,field_info|
  p field_info.header
  Date.parse(field)
end
p csv.first

# => "date1"
# => "date2"
# => #<CSV::Row "date1":#<Date: 2018-07-09 ((2458309j,0s,0n),+0s,2299161j)> "date2":#<Date: 2018-07-10 ((2458310j,0s,0n),+0s,2299161j)>>