require 'hashie/hash' require 'set' module Hashie # A Dash is a 'defined' or 'discrete' Hash, that is, a Hash # that has a set of defined keys that are accessible (with # optional defaults) and only those keys may be set or read. # # 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. # # It is preferrable to a Struct because of the in-class # API for defining properties as well as per-property defaults. class Dash < Hash include Hashie::Extensions::PrettyInspect alias to_s inspect # Defines a property on the Dash. Options are # as follows: # # * :default - Specify a default value for this property, # to be returned before a value is set on the property in a new # Dash. # # * :required - Specify the value as required for this # property, to raise an error if a value is unset in a new or # existing Dash. If a Proc is provided, it will be run in the # context of the Dash instance. If a Symbol is provided, the # property it represents must not be nil. The property is only # required if the value is truthy. # # * :message - Specify custom error message for required property # def self.property(property_name, options = {}) properties << property_name if options.key?(:default) defaults[property_name] = options[:default] elsif defaults.key?(property_name) defaults.delete property_name end define_getter_for(property_name) define_setter_for(property_name) @subclasses.each { |klass| klass.property(property_name, options) } if defined? @subclasses condition = options.delete(:required) if condition message = options.delete(:message) || "is required for #{name}." required_properties[property_name] = { condition: condition, message: message } elsif options.key?(:message) raise ArgumentError, 'The :message option should be used with :required option.' end end class << self attr_reader :properties, :defaults attr_reader :getters attr_reader :required_properties end instance_variable_set('@properties', Set.new) instance_variable_set('@getters', Set.new) instance_variable_set('@defaults', {}) instance_variable_set('@required_properties', {}) def self.inherited(klass) super (@subclasses ||= Set.new) << klass klass.instance_variable_set('@properties', properties.dup) klass.instance_variable_set('@getters', getters.dup) klass.instance_variable_set('@defaults', defaults.dup) klass.instance_variable_set('@required_properties', required_properties.dup) end # Check to see if the specified property has already been # defined. def self.property?(name) properties.include? name end # Check to see if the specified property is # required. def self.required?(name) required_properties.key? name end private_class_method def self.define_getter_for(property_name) return if getters.include?(property_name) define_method(property_name) { |&block| self.[](property_name, &block) } getters << property_name end private_class_method def self.define_setter_for(property_name) setter = :"#{property_name}=" return if instance_methods.include?(setter) define_method(setter) { |value| self.[]=(property_name, value) } end # You may initialize a Dash with an attributes hash # just like you would many other kinds of data objects. def initialize(attributes = {}, &block) super(&block) initialize_attributes(attributes) assert_required_attributes_set! end alias _regular_reader [] alias _regular_writer []= private :_regular_reader, :_regular_writer # Retrieve a value from the Dash (will return the # property's default value if it hasn't been set). def [](property) assert_property_exists! property value = super(property) # If the value is a lambda, proc, or whatever answers to call, eval the thing! if value.is_a? Proc self[property] = value.call # Set the result of the call as a value else yield value if block_given? value end end # Set a value on the Dash in a Hash-like way. Only works # on pre-existing properties. def []=(property, value) assert_property_required! property, value assert_property_exists! property super(property, value) end def merge(other_hash) new_dash = dup other_hash.each do |k, v| new_dash[k] = block_given? ? yield(k, self[k], v) : v end new_dash end def merge!(other_hash) other_hash.each do |k, v| self[k] = block_given? ? yield(k, self[k], v) : v end self end def replace(other_hash) other_hash = self.class.defaults.merge(other_hash) (keys - other_hash.keys).each { |key| delete(key) } other_hash.each { |key, value| self[key] = value } self end def to_h defaults = ::Hash[self.class.properties.map { |prop| [prop, self.class.defaults[prop]] }] defaults.merge(self) end alias to_hash to_h def update_attributes!(attributes) update_attributes(attributes) self.class.defaults.each_pair do |prop, value| next unless fetch(prop, nil).nil? self[prop] = begin val = value.dup if val.is_a?(Proc) val.arity == 1 ? val.call(self) : val.call else val end rescue TypeError value end end assert_required_attributes_set! end private def initialize_attributes(attributes) return unless attributes cleaned_attributes = attributes.reject { |_attr, value| value.nil? } update_attributes!(cleaned_attributes) end def update_attributes(attributes) return unless attributes attributes.each_pair do |att, value| self[att] = value end end def assert_property_exists!(property) fail_no_property_error!(property) unless self.class.property?(property) end def assert_required_attributes_set! self.class.required_properties.each_key do |required_property| assert_property_set!(required_property) end end def assert_property_set!(property) fail_property_required_error!(property) if send(property).nil? && required?(property) end def assert_property_required!(property, value) fail_property_required_error!(property) if value.nil? && required?(property) end def fail_property_required_error!(property) raise ArgumentError, "The property '#{property}' #{self.class.required_properties[property][:message]}" end def fail_no_property_error!(property) raise NoMethodError, "The property '#{property}' is not defined for #{self.class.name}." end def required?(property) return false unless self.class.required?(property) condition = self.class.required_properties[property][:condition] case condition when Proc then !!instance_exec(&condition) when Symbol then !!send(condition) else !!condition end end end end