Class: CSV::Row

Inherits:
Object
  • Object
show all
Extended by:
Forwardable
Includes:
Enumerable
Defined in:
lib/csv.rb

Overview

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.

Instance Method Summary collapse

Constructor Details

#initialize(headers, fields, header_row = false) ⇒ Row

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 CSV::Row.header_row?() and CSV::Row.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()


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# File 'lib/csv.rb', line 237

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
    headers.zip(fields)
  else
    fields.zip(headers).map { |pair| pair.reverse! }
  end
end

Instance Method Details

#<<(arg) ⇒ Object

:call-seq:

<<( field )
<<( 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.


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# File 'lib/csv.rb', line 382

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]
  end

  self  # for chaining
end

#==(other) ⇒ Object

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


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# File 'lib/csv.rb', line 519

def ==(other)
  return @row == other.row if other.is_a? CSV::Row
  @row == other
end

#[]=(*args) ⇒ Object

:call-seq:

[]=( header, value )
[]=( header, offset, value )
[]=( index, value )

Looks up the field by the semantics described in CSV::Row.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.


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# File 'lib/csv.rb', line 349

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]
      @row.map! { |pair| pair.nil? ? [nil, nil] : pair }
    else                      # normal index assignment
      @row[args.first][1] = value
    end
  else
    index = index(*args)
    if index.nil?             # appending a field
      self << [args.first, value]
    else                      # normal header assignment
      @row[index][1] = value
    end
  end
end

#delete(header_or_index, minimum_index = 0) ⇒ Object

:call-seq:

delete( header )
delete( header, offset )
delete( index )

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


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# File 'lib/csv.rb', line 417

def delete(header_or_index, minimum_index = 0)
  if header_or_index.is_a? Integer                 # by index
    @row.delete_at(header_or_index)
  elsif i = index(header_or_index, minimum_index)  # by header
    @row.delete_at(i)
  else
    [ ]
  end
end

#delete_if(&block) ⇒ Object

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.


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# File 'lib/csv.rb', line 434

def delete_if(&block)
  @row.delete_if(&block)

  self  # for chaining
end

#each(&block) ⇒ Object

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.


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# File 'lib/csv.rb', line 509

def each(&block)
  @row.each(&block)

  self  # for chaining
end

#fetch(header, *varargs) ⇒ Object

:call-seq:

fetch( header )
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.

Raises:

  • (ArgumentError)

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# File 'lib/csv.rb', line 312

def fetch(header, *varargs)
  raise ArgumentError, "Too many arguments" if varargs.length > 1
  pair = @row.assoc(header)
  if pair
    pair.last
  else
    if block_given?
      yield header
    elsif varargs.empty?
      raise KeyError, "key not found: #{header}"
    else
      varargs.first
    end
  end
end

#field(header_or_index, minimum_index = 0) ⇒ Object Also known as: []

:call-seq:

field( header )
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.


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# File 'lib/csv.rb', line 286

def field(header_or_index, minimum_index = 0)
  # locate the pair
  finder = (header_or_index.is_a?(Integer) || header_or_index.is_a?(Range)) ? :[] : :assoc
  pair   = @row[minimum_index..-1].send(finder, header_or_index)

  # return the field if we have a pair
  if pair.nil?
    nil
  else
    header_or_index.is_a?(Range) ? pair.map(&:last) : pair.last
  end
end

#field?(data) ⇒ Boolean

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

Returns:

  • (Boolean)

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# File 'lib/csv.rb', line 495

def field?(data)
  fields.include? data
end

#field_row?Boolean

Returns true if this is a field row.

Returns:

  • (Boolean)

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# File 'lib/csv.rb', line 264

def field_row?
  not header_row?
end

#fields(*headers_and_or_indices) ⇒ Object Also known as: values_at

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 CSV::Row.field().

If called with no arguments, all fields are returned.


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# File 'lib/csv.rb', line 448

def fields(*headers_and_or_indices)
  if headers_and_or_indices.empty?  # return all fields--no arguments
    @row.map { |pair| pair.last }
  else                              # or work like values_at()
    headers_and_or_indices.inject(Array.new) 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(h_or_i.begin)
        index_end   = h_or_i.end.is_a?(Integer)   ? h_or_i.end :
                                                    index(h_or_i.end)
        new_range   = h_or_i.exclude_end? ? (index_begin...index_end) :
                                            (index_begin..index_end)
        fields.values_at(new_range)
      else
        [field(*Array(h_or_i))]
      end
    end
  end
end

#has_key?(header) ⇒ Boolean Also known as: key?, member?

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

Returns:

  • (Boolean)

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# File 'lib/csv.rb', line 329

def has_key?(header)
  !!@row.assoc(header)
end

#header?(name) ⇒ Boolean Also known as: include?

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

Returns:

  • (Boolean)

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# File 'lib/csv.rb', line 486

def header?(name)
  headers.include? name
end

#header_row?Boolean

Returns true if this is a header row.

Returns:

  • (Boolean)

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# File 'lib/csv.rb', line 259

def header_row?
  @header_row
end

#headersObject

Returns the headers of this row.


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# File 'lib/csv.rb', line 269

def headers
  @row.map { |pair| pair.first }
end

#index(header, minimum_index = 0) ⇒ Object

:call-seq:

index( header )
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 CSV::Row.field().


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# File 'lib/csv.rb', line 478

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
end

#inspectObject

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


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# File 'lib/csv.rb', line 544

def inspect
  str = ["#<", self.class.to_s]
  each do |header, field|
    str << " " << (header.is_a?(Symbol) ? header.to_s : header.inspect) <<
           ":" << field.inspect
  end
  str << ">"
  begin
    str.join('')
  rescue  # any encoding error
    str.map do |s|
      e = Encoding::Converter.asciicompat_encoding(s.encoding)
      e ? s.encode(e) : s.force_encoding("ASCII-8BIT")
    end.join('')
  end
end

#push(*args) ⇒ Object

A shortcut for appending multiple fields. Equivalent to:

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

This method returns the row for chaining.


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# File 'lib/csv.rb', line 401

def push(*args)
  args.each { |arg| self << arg }

  self  # for chaining
end

#to_csv(options = Hash.new) ⇒ Object Also known as: to_s

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

csv_row.fields.to_csv( options )

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# File 'lib/csv.rb', line 538

def to_csv(options = Hash.new)
  fields.to_csv(options)
end

#to_hashObject

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


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# File 'lib/csv.rb', line 528

def to_hash
  # flatten just one level of the internal Array
  Hash[*@row.inject(Array.new) { |ary, pair| ary.push(*pair) }]
end