Parameters

require 'parameters'

class Octagon

  include Parameters

  #
  # A parameter with a default value
  #
  parameter :x, :default => 0

  #
  # Another parameter with a default value
  #
  parameter :y, :default => 0.5

  #
  # A parameter with an enforced type and description.
  #
  # Availble types are: Array[Class], Array, Set[Class], Set,
  # URI, Regexp, DateTime, Date, Symbol, String, Integer, Float
  # and true (for boolean types).
  #
  parameter :radius, :type        => Float,
                     :description => 'The radius of the Octagon'

  #
  # A parameter with a lambda for a default value
  #
  parameter :opacity, :default     => lambda { rand },
                      :description => 'The opacity of the Octagon'

end

# Create an object with default values for all parameters
oct = Octagon.new
oct.x       # => 0
oct.y       # => 0.5
oct.opacity # => 0.25

# Create an object with the given parameter values.
oct = Octagon.new(:radius => 10)
oct.radius  # => 10
oct.opacity # => 0.7

# Set parameter values of a class
Octagon.radius = 33
Octagon.opacity = 0.3

# Create an object with parameter defaulte values inherited from the
# class parameters
oct = Octagon.new
oct.radius  # => 33
oct.opacity # => 0.3

# Coerce data from the command-line into the given parameter type
oct.radius = ARGV[2]
oct.radius # => 89.455

$ gem install parameters