Module: Value

Defined in:
lib/value-1.0.rb,
lib/value-1.0/version.rb

Overview

Represents an immutable [value object](en.wikipedia.org/wiki/Value_object) with an #initialize method, equality checks #== and #eql?, a #hash function, and an #inspect method.

Examples:

A Point Value Object

class Point
  Value :x, :y
end

A Point Value Object with Public Accessors

class Point
  Value :x, :y
  public(*attributes)
end

A Value Object with Optional Attributes

class Money
  Value :amount, [:currency, :USD]
end

A Value Object with a Comparable Attribute

class Vector
  Value :a, :b, :comparable => :a
end

Defined Under Namespace

Modules: Comparable Classes: Attributes

Constant Summary collapse

Version = 
Inventory.new(1, 1, 3){
  authors{
    author 'Nikolai Weibull', '[email protected]'
  }

  homepage 'http://disu.se/software/value'

  licenses{
    license 'LGPLv3+',
            'GNU Lesser General Public License, version 3 or later',
            'http://www.gnu.org/licenses/'
  }

  def dependencies
    super + Inventory::Dependencies.new{
      development 'inventory-rake', 1, 6, 0
      development 'inventory-rake-tasks-yard', 1, 4, 0
      development 'lookout', 3, 0, 0
      development 'lookout-rake', 3, 1, 0
      development 'yard', 0, 8, 0
      development 'yard-heuristics', 1, 2, 0
    }
  end

  def package_libs
    %w[attributes.rb
       comparable.rb]
  end
}

Instance Method Summary collapse

Instance Method Details

#==(other) ⇒ Boolean Also known as: eql?

Returns True if the receiver’s class and all of its Attributes ‘#==` those of OTHER.

Returns:

  • (Boolean) —

    True if the receiver’s class and all of its Attributes ‘#==` those of OTHER



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# File 'lib/value-1.0.rb', line 69

def ==(other)
  self.class == other.class and attributes.all?{ |e| send(e) == other.send(e) }
end

#hash ⇒ Fixnum

Returns The hash value of the receiver’s class XORed with the hash value of the Array of the values of the Attributes of the receiver.

Returns:

  • (Fixnum) —

    The hash value of the receiver’s class XORed with the hash value of the Array of the values of the Attributes of the receiver



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# File 'lib/value-1.0.rb', line 78

def hash
  self.class.hash ^ attributes.map{ |e| send(e) }.hash
end

#initialize(*arguments) {|?| ... } ⇒ Object

Creates a new value object, using ARGUMENTS to set up the value’s required, optional, and splat attributes, and the given block, if given, if a block is desired.

Parameters:

  • arguments (Object, …)

Yields:

  • (?)

Raises:

  • (ArgumentError) —

    If ARGUMENTS#length is less than the number of required attributes

  • (ArgumentError) —

    If ARGUMENTS#length is greater than the number of required and optional attributes



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# File 'lib/value-1.0.rb', line 41

def initialize(*arguments)
  raise ArgumentError,
    'wrong number of arguments (%d for %d)' %
      [arguments.length, attributes.required.length] if
        arguments.length < attributes.required.length
  raise ArgumentError,
    'wrong number of arguments (%d for %d)' %
      [arguments.length,
       attributes.required.length + attributes.optional.length] if
        arguments.length > attributes.required.length +
          attributes.optional.length and not attributes.splat
  instance_variable_set :"@#{attributes.block}",
    block_given? ? Proc.new : nil if attributes.block
  instance_variable_set :"@#{attributes.splat}",
    arguments[attributes.required.length +
              attributes.optional.length..-1] if attributes.splat
  attributes.required.each_with_index do |value, index|
    instance_variable_set :"@#{value}", arguments[index]
  end
  attributes.optional.each_with_index do |(value, default), index|
    offset = attributes.required.length + index
    instance_variable_set :"@#{value}",
      offset >= arguments.length ? default : arguments[offset]
  end
end

#inspect ⇒ String

Returns The inspection of the receiver.

Returns:

  • (String) —

    The inspection of the receiver



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# File 'lib/value-1.0.rb', line 83

def inspect
  '%s.new(%s)' %
    [self.class,
     [attributes.required.map{ |name| send(name).inspect },
      attributes.optional.
        map{ |name, default| [send(name), default] }.
        select{ |value, default| value != default or attributes.splat }.
        map{ |value, _| value },
      attributes.splat ? send(attributes.splat).map{ |value| value.inspect } : [],
      attributes.block ? ['&%s' % [send(attributes.block).inspect]] : []].
        flatten.join(', ')]
end