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require 'hashie/dash'
module Hashie
# A Lash is just like a Dash, except that a Lash allows
# that properties can set as required. This means that if
# an attempt is made to create a Lash with out it, an error
# will be raised.
#
# Dashes are useful when you need to create a very simple
# lightweight data object that needs even fewer options and
# resources than something like a DataMapper resource, and
# certain attributes are required.
#
# It is preferrable to a Struct because of the in-class
# API for defining properties as well as per-property defaults
# and requirements.
class Lash < Hashie::Dash
# Defines a property on the Lash. Options are
# as follows:
#
# * <tt>:default</tt> - Specify a default value for this property,
# to be returned before a value is set on the property in a new
# Lash.
#
# * <tt>:required</tt> - Specify the value as required for this
# property, to raise an error if a value is unset in a new or
# existing Lash.
#
def self.property(property_name, options = {})
super
required_properties << property_name if options.delete(:required)
end
class << self
attr_reader :required_properties
end
instance_variable_set('@required_properties', Set.new)
def self.inherited(klass)
super
klass.instance_variable_set('@required_properties', self.required_properties.dup)
end
# Check to see if the specified property is
# required.
def self.required?(name)
required_properties.include? name.to_sym
end
# You may initialize a Lash with an attributes hash
# just like you would many other kinds of data objects.
# Remember to pass in the values for the properties
# you set as required.
def initialize(attributes = {}, &block)
super(attributes, &block)
assert_required_properties_set!
end
# Set a value on the Lash in a Hash-like way. Only works
# on pre-existing properties and errors if you try to
# set a required value to nil.
def []=(property, value)
assert_property_required! property, value
super(property.to_s, value)
end
private
def assert_required_properties_set!
self.class.required_properties.each do |required_property|
assert_property_set!(required_property)
end
end
def assert_property_set!(property)
if send(property).nil?
raise ArgumentError, "The property '#{property}' is required for this Lash."
end
end
def assert_property_required!(property, value)
if self.class.required?(property) && value.nil?
raise ArgumentError, "The property '#{property}' is required for this Lash."
end
end
end
end
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