Argument Converters

An option can specify that its argument is to be converted from the default String to an instance of another class.

Contents

• Built-In Argument Converters

  • Date

  • DateTime

  • Time

  • URI

  • Shellwords

  • Integer

  • Float

  • Numeric

  • DecimalInteger

  • OctalInteger

  • DecimalNumeric

  • TrueClass

  • FalseClass

  • Object

  • String

  • Array

  • Regexp

• Custom Argument Converters

Built-In Argument Converters

OptionParser has a number of built-in argument converters, which are demonstrated below.

Date

File date.rb defines an option whose argument is to be converted to a Date object. The argument is converted by method Date#parse.

require 'optparse/date'
parser = OptionParser.new
parser.on('--date=DATE', Date) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby date.rb --date 2001-02-03
[#<Date: 2001-02-03 ((2451944j,0s,0n),+0s,2299161j)>, Date]
$ ruby date.rb --date 20010203
[#<Date: 2001-02-03 ((2451944j,0s,0n),+0s,2299161j)>, Date]
$ ruby date.rb --date "3rd Feb 2001"
[#<Date: 2001-02-03 ((2451944j,0s,0n),+0s,2299161j)>, Date]

DateTime

File datetime.rb defines an option whose argument is to be converted to a DateTime object. The argument is converted by method DateTime#parse.

require 'optparse/date'
parser = OptionParser.new
parser.on('--datetime=DATETIME', DateTime) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby datetime.rb --datetime 2001-02-03T04:05:06+07:00
[#<DateTime: 2001-02-03T04:05:06+07:00 ((2451943j,75906s,0n),+25200s,2299161j)>, DateTime]
$ ruby datetime.rb --datetime 20010203T040506+0700
[#<DateTime: 2001-02-03T04:05:06+07:00 ((2451943j,75906s,0n),+25200s,2299161j)>, DateTime]
$ ruby datetime.rb --datetime "3rd Feb 2001 04:05:06 PM"
[#<DateTime: 2001-02-03T16:05:06+00:00 ((2451944j,57906s,0n),+0s,2299161j)>, DateTime]

Time

File time.rb defines an option whose argument is to be converted to a Time object. The argument is converted by method Time#httpdate or Time#parse.

require 'optparse/time'
parser = OptionParser.new
parser.on('--time=TIME', Time) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby time.rb --time "Thu, 06 Oct 2011 02:26:12 GMT"
[2011-10-06 02:26:12 UTC, Time]
$ ruby time.rb --time 2010-10-31
[2010-10-31 00:00:00 -0500, Time]

URI

File uri.rb defines an option whose argument is to be converted to a URI object. The argument is converted by method URI#parse.

require 'optparse/uri'
parser = OptionParser.new
parser.on('--uri=URI', URI) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby uri.rb --uri https://github.com
[#<URI::HTTPS https://github.com>, URI::HTTPS]
$ ruby uri.rb --uri http://github.com
[#<URI::HTTP http://github.com>, URI::HTTP]
$ ruby uri.rb --uri file://~/var
[#<URI::File file://~/var>, URI::File]

Shellwords

File shellwords.rb defines an option whose argument is to be converted to an Array object by method Shellwords#shellwords.

require 'optparse/shellwords'
parser = OptionParser.new
parser.on('--shellwords=SHELLWORDS', Shellwords) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby shellwords.rb --shellwords "ruby my_prog.rb | less"
[["ruby", "my_prog.rb", "|", "less"], Array]
$ ruby shellwords.rb --shellwords "here are 'two words'"
[["here", "are", "two words"], Array]

Integer

File integer.rb defines an option whose argument is to be converted to an Integer object. The argument is converted by method Kernel#Integer.

require 'optparse'
parser = OptionParser.new
parser.on('--integer=INTEGER', Integer) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby integer.rb --integer 100
[100, Integer]
$ ruby integer.rb --integer -100
[-100, Integer]
$ ruby integer.rb --integer 0100
[64, Integer]
$ ruby integer.rb --integer 0x100
[256, Integer]
$ ruby integer.rb --integer 0b100
[4, Integer]

Float

File float.rb defines an option whose argument is to be converted to a Float object. The argument is converted by method Kernel#Float.

require 'optparse'
parser = OptionParser.new
parser.on('--float=FLOAT', Float) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby float.rb --float 1
[1.0, Float]
$ ruby float.rb --float 3.14159
[3.14159, Float]
$ ruby float.rb --float 1.234E2
[123.4, Float]
$ ruby float.rb --float 1.234E-2
[0.01234, Float]

Numeric

File numeric.rb defines an option whose argument is to be converted to an instance of Rational, Float, or Integer. The argument is converted by method Kernel#Rational, Kernel#Float, or Kernel#Integer.

require 'optparse'
parser = OptionParser.new
parser.on('--numeric=NUMERIC', Numeric) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby numeric.rb --numeric 1/3
[(1/3), Rational]
$ ruby numeric.rb --numeric 3.333E-1
[0.3333, Float]
$ ruby numeric.rb --numeric 3
[3, Integer]

DecimalInteger

File decimal_integer.rb defines an option whose argument is to be converted to an Integer object. The argument is converted by method Kernel#Integer.

require 'optparse'
include OptionParser::Acceptables
parser = OptionParser.new
parser.on('--decimal_integer=DECIMAL_INTEGER', DecimalInteger) do |value|
  p [value, value.class]
end
parser.parse!

The argument may not be in a binary or hexadecimal format; a leading zero is ignored (not parsed as octal).

Executions:

$ ruby decimal_integer.rb --decimal_integer 100
[100, Integer]
$ ruby decimal_integer.rb --decimal_integer -100
[-100, Integer]
$ ruby decimal_integer.rb --decimal_integer 0100
[100, Integer]
$ ruby decimal_integer.rb --decimal_integer -0100
[-100, Integer]

OctalInteger

File octal_integer.rb defines an option whose argument is to be converted to an Integer object. The argument is converted by method Kernel#Integer.

require 'optparse'
include OptionParser::Acceptables
parser = OptionParser.new
parser.on('--octal_integer=OCTAL_INTEGER', OctalInteger) do |value|
  p [value, value.class]
end
parser.parse!

The argument may not be in a binary or hexadecimal format; it is parsed as octal, regardless of whether it has a leading zero.

Executions:

$ ruby octal_integer.rb --octal_integer 100
[64, Integer]
$ ruby octal_integer.rb --octal_integer -100
[-64, Integer]
$ ruby octal_integer.rb --octal_integer 0100
[64, Integer]

DecimalNumeric

File decimal_numeric.rb defines an option whose argument is to be converted to an Integer object. The argument is converted by method Kernel#Integer

require 'optparse'
include OptionParser::Acceptables
parser = OptionParser.new
parser.on('--decimal_numeric=DECIMAL_NUMERIC', DecimalNumeric) do |value|
  p [value, value.class]
end
parser.parse!

The argument may not be in a binary or hexadecimal format; a leading zero causes the argument to be parsed as octal.

Executions:

$ ruby decimal_numeric.rb --decimal_numeric 100
[100, Integer]
$ ruby decimal_numeric.rb --decimal_numeric -100
[-100, Integer]
$ ruby decimal_numeric.rb --decimal_numeric 0100
[64, Integer]

TrueClass

File true_class.rb defines an option whose argument is to be converted to true or false. The argument is evaluated by method Object#nil?.

require 'optparse'
parser = OptionParser.new
parser.on('--true_class=TRUE_CLASS', TrueClass) do |value|
  p [value, value.class]
end
parser.parse!

The argument may be any of those shown in the examples below.

Executions:

$ ruby true_class.rb --true_class true
[true, TrueClass]
$ ruby true_class.rb --true_class yes
[true, TrueClass]
$ ruby true_class.rb --true_class +
[true, TrueClass]
$ ruby true_class.rb --true_class false
[false, FalseClass]
$ ruby true_class.rb --true_class no
[false, FalseClass]
$ ruby true_class.rb --true_class -
[false, FalseClass]
$ ruby true_class.rb --true_class nil
[false, FalseClass]

FalseClass

File false_class.rb defines an option whose argument is to be converted to true or false. The argument is evaluated by method Object#nil?.

require 'optparse'
parser = OptionParser.new
parser.on('--false_class=FALSE_CLASS', FalseClass) do |value|
  p [value, value.class]
end
parser.parse!

The argument may be any of those shown in the examples below.

Executions:

$ ruby false_class.rb --false_class false
[false, FalseClass]
$ ruby false_class.rb --false_class no
[false, FalseClass]
$ ruby false_class.rb --false_class -
[false, FalseClass]
$ ruby false_class.rb --false_class nil
[false, FalseClass]
$ ruby false_class.rb --false_class true
[true, TrueClass]
$ ruby false_class.rb --false_class yes
[true, TrueClass]
$ ruby false_class.rb --false_class +
[true, TrueClass]

Object

File object.rb defines an option whose argument is not to be converted from String.

require 'optparse'
parser = OptionParser.new
parser.on('--object=OBJECT', Object) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby object.rb --object foo
["foo", String]
$ ruby object.rb --object nil
["nil", String]

String

File string.rb defines an option whose argument is not to be converted from String.

require 'optparse'
parser = OptionParser.new
parser.on('--string=STRING', String) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby string.rb --string foo
["foo", String]
$ ruby string.rb --string nil
["nil", String]

Array

File array.rb defines an option whose argument is to be converted from String to an array of strings, based on comma-separated substrings.

require 'optparse'
parser = OptionParser.new
parser.on('--array=ARRAY', Array) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby array.rb --array ""
[[], Array]
$ ruby array.rb --array foo,bar,baz
[["foo", "bar", "baz"], Array]
$ ruby array.rb --array "foo, bar, baz"
[["foo", " bar", " baz"], Array]

Regexp

File regexp.rb defines an option whose argument is to be converted to a Regexp object.

require 'optparse'
parser = OptionParser.new
parser.on('--regexp=REGEXP', Regexp) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby regexp.rb --regexp foo

Custom Argument Converters

You can create custom argument converters. To create a custom converter, call OptionParser#accept with:

• An identifier, which may be any object.

• An optional match pattern, which defaults to /.*/m.

• A block that accepts the argument and returns the converted value.

This custom converter accepts any argument and converts it, if possible, to a Complex object.

require 'optparse/date'
parser = OptionParser.new
parser.accept(Complex) do |value|
  value.to_c
end
parser.on('--complex COMPLEX', Complex) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby custom_converter.rb --complex 0
[(0+0i), Complex]
$ ruby custom_converter.rb --complex 1
[(1+0i), Complex]
$ ruby custom_converter.rb --complex 1+2i
[(1+2i), Complex]
$ ruby custom_converter.rb --complex 0.3-0.5i
[(0.3-0.5i), Complex]

This custom converter accepts any 1-word argument and capitalizes it, if possible.

require 'optparse/date'
parser = OptionParser.new
parser.accept(:capitalize, /\w*/) do |value|
  value.capitalize
end
parser.on('--capitalize XXX', :capitalize) do |value|
  p [value, value.class]
end
parser.parse!

Executions:

$ ruby match_converter.rb --capitalize foo
["Foo", String]
$ ruby match_converter.rb --capitalize "foo bar"
match_converter.rb:9:in `<main>': invalid argument: --capitalize foo bar (OptionParser::InvalidArgument)

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