Class: CSV::Row

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

Constructs 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 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/row.rb', line 30

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).each(&: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/row.rb', line 181

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/row.rb', line 322

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/row.rb', line 148

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 )

Removes 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/row.rb', line 216

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.

If no block is given, an Enumerator is returned.


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# File 'lib/csv/row.rb', line 235

def delete_if(&block)
  return enum_for(__method__) { size } unless block_given?

  @row.delete_if(&block)

  self  # for chaining
end

#dig(index_or_header, *indexes) ⇒ Object

Extracts the nested value specified by the sequence of index or header objects by calling dig at each step, returning nil if any intermediate step is nil.


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# File 'lib/csv/row.rb', line 356

def dig(index_or_header, *indexes)
  value = field(index_or_header)
  if value.nil?
    nil
  elsif indexes.empty?
    value
  else
    unless value.respond_to?(:dig)
      raise TypeError, "#{value.class} does not have \#dig method"
    end
    value.dig(*indexes)
  end
end

#each(&block) ⇒ Object Also known as: each_pair

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

If no block is given, an Enumerator is returned.

Support for Enumerable.


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# File 'lib/csv/row.rb', line 308

def each(&block)
  return enum_for(__method__) { size } unless block_given?

  @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/row.rb', line 110

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/row.rb', line 84

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.


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# File 'lib/csv/row.rb', line 294

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

#field_row?Boolean

Returns true if this is a field row.


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# File 'lib/csv/row.rb', line 62

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/row.rb', line 251

def fields(*headers_and_or_indices)
  if headers_and_or_indices.empty?  # return all fields--no arguments
    @row.map(&:last)
  else                              # or work like values_at()
    all = []
    headers_and_or_indices.each do |h_or_i|
      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)
        all.concat(fields.values_at(new_range))
      else
        all << field(*Array(h_or_i))
      end
    end
    return all
  end
end

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

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


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# File 'lib/csv/row.rb', line 127

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

#header_row?Boolean

Returns true if this is a header row.


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# File 'lib/csv/row.rb', line 57

def header_row?
  @header_row
end

#headersObject

Returns the headers of this row.


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# File 'lib/csv/row.rb', line 67

def headers
  @row.map(&: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/row.rb', line 283

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

#initialize_copy(other) ⇒ Object


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# File 'lib/csv/row.rb', line 51

def initialize_copy(other)
  super
  @row = @row.dup
end

#inspectObject

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


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# File 'lib/csv/row.rb', line 373

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/row.rb', line 200

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

  self  # for chaining
end

#to_csv(**options) ⇒ 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/row.rb', line 347

def to_csv(**options)
  fields.to_csv(**options)
end

#to_hObject Also known as: to_hash

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/row.rb', line 331

def to_h
  hash = {}
  each do |key, _value|
    hash[key] = self[key] unless hash.key?(key)
  end
  hash
end