class CSVobj

This class represents each row of a CSV file as an object in an array. Object attributes are automatically created from the header (first) row in the CSV. Note that this class dynamically redefines its own attributes and constructor so you should subclass it for any remotely serious work.

Public Class Methods

header_to_attr(header) click to toggle source

Convert a header (string) value to a an attribute symbol: Remove leading and trailing whitespace; replace (repeated) non-word characters with a single underscore; prefix leading digit with underscore; remove repeated adjacent underscores; convert to a lower-case symbol.

# File lib/csvobj.rb, line 75
def self.header_to_attr(header)
  header.strip. # remove trailing and leading whitespace
    gsub(/\W+/, '_').  # substitute underscore for non-word/digit characters
    sub(/^(\d)/, '_\1'). # if starts with a digit insert a leading underscore
    gsub(/_+/, '_'). # remove duplicate adjacent underscores
    downcase. # convert to lower case
    to_sym # convert to symbol
end

parse(csv) click to toggle source

Parse the given CSV, which may be a multi-line string or IO object (see parse_s) or an array of row arrays (see parse_a) and return an array of CSVobjs. Expects the first row to be the headers (these are used for the objects’ attributes).

# File lib/csvobj.rb, line 22
def self.parse(csv)
  csv.is_a?(Array) ? parse_a(csv) : parse_s(csv)
end

parse_a(rows) click to toggle source

Interpret an array (rows) of arrays (cells) and return an array of CSVobjs. Expects the first row to be the headers (these are used for the objects’ attributes).

# File lib/csvobj.rb, line 39
def self.parse_a(rows)
  return [] if rows.empty?

  # Get attributes from first row.
  headers = rows.shift
  attr_symbols = headers.map{ |header| header_to_attr(header) }
  dupes = attr_symbols.uniq!
  raise CSVobjDuplicateHeader, "Duplicate derived headers\n#{dupes}" if dupes

  # Declare attributes and constructor. This will take the form:
  #     #new(header1, header2, ...).
  instance_variables = attr_symbols.map{ |attr| "@#{attr}" }
  class_eval do
    attr_accessor(*attr_symbols)
    define_method :initialize do |*args|
      instance_variables.zip(args).each do |instance_variable, arg|
        instance_variable_set(instance_variable, arg)
      end
    end
  end

  # Define class method #headers to return an array of the (unmangled)
  # CSV headers by defining the method on the metaclass.
  (class << self ; self end).send(:define_method, :headers) { headers }

  # Create and return array of CSVobj, one element for each CSV row
  # (minus the headers).
  rows.map { |row| new(*row) }
end

parse_s(csv) click to toggle source

Interpret the given multi-line string or IO object of CSV records and return an array of CSVobjs. Expects the first row to be the headers (these are used for the objects’ attributes).

# File lib/csvobj.rb, line 30
def self.parse_s(csv)
  rows = s_to_a(csv)
  parse_a(rows)
end

Private Class Methods

s_to_a(io_or_string) click to toggle source

Abstraction to deal with ruby 1.8/1.9 CSV incompatibilities. Takes an IO-like object or a string, returns an array of CSV objects.

# File lib/csvobj.rb, line 110
def self.s_to_a(io_or_string)
  if CSV.const_defined?(:Reader) # ruby 1.8
    CSV::Reader.create( io_or_string ).to_a
  else # ruby 1.9 and beyond
    CSV.parse( io_or_string )
  end
end

Public Instance Methods

to_a() click to toggle source

Return an array of (string) values for this CSV object in the order that they were given. See dynamically defined method headers to get the equivalent array of headers.

# File lib/csvobj.rb, line 87
def to_a
  self.class.headers.map do |header|
    attr = self.class.header_to_attr(header)
    send(attr)
  end
end

to_s() click to toggle source

Return a CSV string representing this object. Does not include headers (see to_s_with_headers).

# File lib/csvobj.rb, line 96
def to_s
  a_to_s(to_a)
end

to_s_with_headers() click to toggle source

Return a CSV string representing this object including an initial line of headers as originally given on object creation.

# File lib/csvobj.rb, line 102
def to_s_with_headers
  a_to_s(self.class.headers) + to_s
end

Private Instance Methods

a_to_s(a) click to toggle source

Abstraction to deal with ruby 1.8/1.9 CSV class incompatibilities. Takes an array of values and returns a CSV-encoded string.

# File lib/csvobj.rb, line 120
def a_to_s(a)
  if CSV.const_defined?(:Reader) # ruby 1.8
    (CSV::Writer.generate(s='') << a).close
    s
  else # ruby 1.9 and beyond
    CSV.generate { |csv| csv << a }
  end
end