class CSV::Row

A CSV::Row is part Array and part Hash. It retains an order for the fields and allows duplicates just as an Array would, but also allows you to access fields by name just as you could if they were in a Hash.

All rows returned by CSV will be constructed from this class, if header row processing is activated.



Internal data format used to compare equality.

Public Class Methods

new(headers, fields, header_row = false) click to toggle source

Construct a new CSV::Row from headers and fields, which are expected to be Arrays. If one Array is shorter than the other, it will be padded with nil objects.

The optional header_row parameter can be set to true to indicate, via #header_row? and #field_row?, that this is a header row. Otherwise, the row is assumes to be a field row.

A CSV::Row object supports the following Array methods through delegation:

  • empty?()

  • length()

  • size()

# File lib/csv.rb, line 235
def initialize(headers, fields, header_row = false)
  @header_row = header_row
  headers.each { |h| h.freeze if h.is_a? String }

  # handle extra headers or fields
  @row = if headers.size > fields.size
  else { |pair| pair.reverse }

Public Instance Methods

<<( field ) click to toggle source
<<( header_and_field_array )
<<( header_and_field_hash )

If a two-element Array is provided, it is assumed to be a header and field and the pair is appended. A Hash works the same way with the key being the header and the value being the field. Anything else is assumed to be a lone field which is appended with a nil header.

This method returns the row for chaining.

# File lib/csv.rb, line 376
def <<(arg)
  if arg.is_a?(Array) and arg.size == 2  # appending a header and name
    @row << arg
  elsif arg.is_a?(Hash)                  # append header and name pairs
    arg.each { |pair| @row << pair }
  else                                   # append field value
    @row << [nil, arg]

  self  # for chaining
==(other) click to toggle source

Returns true if this row contains the same headers and fields in the same order as other.

# File lib/csv.rb, line 513
def ==(other)
  return @row == other.row if other.is_a? CSV::Row
  @row == other
[](header_or_index, minimum_index = 0)
Alias for: field
[]=( header, value ) click to toggle source
[]=( header, offset, value )
[]=( index, value )

Looks up the field by the semantics described in #field and assigns the value.

Assigning past the end of the row with an index will set all pairs between to [nil, nil]. Assigning to an unused header appends the new pair.

# File lib/csv.rb, line 343
def []=(*args)
  value = args.pop

  if args.first.is_a? Integer
    if @row[args.first].nil?  # extending past the end with index
      @row[args.first] = [nil, value]! { |pair| pair.nil? ? [nil, nil] : pair }
    else                      # normal index assignment
      @row[args.first][1] = value
    index = index(*args)
    if index.nil?             # appending a field
      self << [args.first, value]
    else                      # normal header assignment
      @row[index][1] = value
delete( header ) click to toggle source
delete( header, offset )
delete( index )

Used to remove a pair from the row by header or index. The pair is located as described in #field. The deleted pair is returned, or nil if a pair could not be found.

# File lib/csv.rb, line 411
def delete(header_or_index, minimum_index = 0)
  if header_or_index.is_a? Integer                 # by index
  elsif i = index(header_or_index, minimum_index)  # by header
    [ ]
delete_if(&block) click to toggle source

The provided block is passed a header and field for each pair in the row and expected to return true or false, depending on whether the pair should be deleted.

This method returns the row for chaining.

# File lib/csv.rb, line 428
def delete_if(&block)

  self  # for chaining
each(&block) click to toggle source

Yields each pair of the row as header and field tuples (much like iterating over a Hash).

Support for Enumerable.

This method returns the row for chaining.

# File lib/csv.rb, line 503
def each(&block)

  self  # for chaining
fetch( header ) click to toggle source
fetch( header ) { |row| ... }
fetch( header, default )

This method will fetch the field value by header. It has the same behavior as Hash#fetch: if there is a field with the given header, its value is returned. Otherwise, if a block is given, it is yielded the header and its result is returned; if a default is given as the second argument, it is returned; otherwise a KeyError is raised.

# File lib/csv.rb, line 306
def fetch(header, *varargs)
  raise ArgumentError, "Too many arguments" if varargs.length > 1
  pair = @row.assoc(header)
  if pair
    if block_given?
      yield header
    elsif varargs.empty?
      raise KeyError, "key not found: #{header}"
field( header ) click to toggle source
field( header, offset )
field( index )

This method will return the field value by header or index. If a field is not found, nil is returned.

When provided, offset ensures that a header match occurs on or later than the offset index. You can use this to find duplicate headers, without resorting to hard-coding exact indices.

# File lib/csv.rb, line 284
def field(header_or_index, minimum_index = 0)
  # locate the pair
  finder = header_or_index.is_a?(Integer) ? :[] : :assoc
  pair   = @row[minimum_index..-1].send(finder, header_or_index)

  # return the field if we have a pair
  pair.nil? ? nil : pair.last
Also aliased as: []
field?(data) click to toggle source

Returns true if data matches a field in this row, and false otherwise.

# File lib/csv.rb, line 489
def field?(data)
  fields.include? data
field_row?() click to toggle source

Returns true if this is a field row.

# File lib/csv.rb, line 262
def field_row?
  not header_row?
fields(*headers_and_or_indices) click to toggle source

This method accepts any number of arguments which can be headers, indices, Ranges of either, or two-element Arrays containing a header and offset. Each argument will be replaced with a field lookup as described in #field.

If called with no arguments, all fields are returned.

# File lib/csv.rb, line 442
def fields(*headers_and_or_indices)
  if headers_and_or_indices.empty?  # return all fields--no arguments { |pair| pair.last }
  else                              # or work like values_at()
    headers_and_or_indices.inject( do |all, h_or_i|
      all + if h_or_i.is_a? Range
        index_begin = h_or_i.begin.is_a?(Integer) ? h_or_i.begin :
        index_end   = h_or_i.end.is_a?(Integer)   ? h_or_i.end :
        new_range   = h_or_i.exclude_end? ? (index_begin...index_end) :
Also aliased as: values_at
has_key?(header) click to toggle source

Returns true if there is a field with the given header.

# File lib/csv.rb, line 323
def has_key?(header)
Also aliased as: include?, key?, member?
header?(name) click to toggle source

Returns true if name is a header for this row, and false otherwise.

# File lib/csv.rb, line 480
def header?(name)
  headers.include? name
Also aliased as: include?
header_row?() click to toggle source

Returns true if this is a header row.

# File lib/csv.rb, line 257
def header_row?
headers() click to toggle source

Returns the headers of this row.

# File lib/csv.rb, line 267
def headers { |pair| pair.first }
Alias for: has_key?
index( header ) click to toggle source
index( header, offset )

This method will return the index of a field with the provided header. The offset can be used to locate duplicate header names, as described in #field.

# File lib/csv.rb, line 472
def index(header, minimum_index = 0)
  # find the pair
  index = headers[minimum_index..-1].index(header)
  # return the index at the right offset, if we found one
  index.nil? ? nil : index + minimum_index
inspect() click to toggle source

A summary of fields, by header, in an ASCII compatible String.

# File lib/csv.rb, line 538
def inspect
  str = ["#<", self.class.to_s]
  each do |header, field|
    str << " " << (header.is_a?(Symbol) ? header.to_s : header.inspect) <<
           ":" << field.inspect
  str << ">"
  rescue  # any encoding error do |s|
      e = Encoding::Converter.asciicompat_encoding(s.encoding)
      e ? s.encode(e) : s.force_encoding("ASCII-8BIT")
Alias for: has_key?
Alias for: has_key?
push(*args) click to toggle source

A shortcut for appending multiple fields. Equivalent to:

args.each { |arg| csv_row << arg }

This method returns the row for chaining.

# File lib/csv.rb, line 395
def push(*args)
  args.each { |arg| self << arg }

  self  # for chaining
to_csv(options = click to toggle source

Returns the row as a CSV String. Headers are not used. Equivalent to:

csv_row.fields.to_csv( options )
# File lib/csv.rb, line 532
def to_csv(options =
Also aliased as: to_s
to_hash() click to toggle source

Collapses the row into a simple Hash. Be warning that this discards field order and clobbers duplicate fields.

# File lib/csv.rb, line 522
def to_hash
  # flatten just one level of the internal Array
  Hash[*@row.inject( { |ary, pair| ary.push(*pair) }]
to_s(options =
Alias for: to_csv
Alias for: fields