class Hashie::Dash
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.
Attributes
Public Class Methods
# File lib/hashie/dash.rb, line 69 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
You may initialize a Dash
with an attributes hash just like you would many other kinds of data objects.
# File lib/hashie/dash.rb, line 104 def initialize(attributes = {}, &block) super(&block) self.class.defaults.each_pair do |prop, value| 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 initialize_attributes(attributes) assert_required_attributes_set! end
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 newDash
. -
:required
- Specify the value as required for this property, to raise an error if a value is unset in a new or existingDash
. If a Proc is provided, it will be run in the context of theDash
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
# File lib/hashie/dash.rb, line 36 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
Check to see if the specified property has already been defined.
# File lib/hashie/dash.rb, line 80 def self.property?(name) properties.include? name end
Check to see if the specified property is required.
# File lib/hashie/dash.rb, line 86 def self.required?(name) required_properties.key? name end
Private Class Methods
# File lib/hashie/dash.rb, line 90 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
# File lib/hashie/dash.rb, line 96 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
Public Instance Methods
Retrieve a value from the Dash
(will return the property's default value if it hasn't been set).
# File lib/hashie/dash.rb, line 130 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.
# File lib/hashie/dash.rb, line 144 def []=(property, value) assert_property_required! property, value assert_property_exists! property super(property, value) end
# File lib/hashie/dash.rb, line 150 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
# File lib/hashie/dash.rb, line 158 def merge!(other_hash) other_hash.each do |k, v| self[k] = block_given? ? yield(k, self[k], v) : v end self end
# File lib/hashie/dash.rb, line 165 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
# File lib/hashie/dash.rb, line 172 def update_attributes!(attributes) update_attributes(attributes) self.class.defaults.each_pair do |prop, value| next unless self[prop].nil? self[prop] = begin value.dup rescue TypeError value end end assert_required_attributes_set! end
Private Instance Methods
# File lib/hashie/dash.rb, line 203 def assert_property_exists!(property) fail_no_property_error!(property) unless self.class.property?(property) end
# File lib/hashie/dash.rb, line 217 def assert_property_required!(property, value) fail_property_required_error!(property) if value.nil? && required?(property) end
# File lib/hashie/dash.rb, line 213 def assert_property_set!(property) fail_property_required_error!(property) if send(property).nil? && required?(property) end
# File lib/hashie/dash.rb, line 207 def assert_required_attributes_set! self.class.required_properties.each_key do |required_property| assert_property_set!(required_property) end end
# File lib/hashie/dash.rb, line 226 def fail_no_property_error!(property) raise NoMethodError, "The property '#{property}' is not defined for #{self.class.name}." end
# File lib/hashie/dash.rb, line 221 def fail_property_required_error!(property) raise ArgumentError, "The property '#{property}' #{self.class.required_properties[property][:message]}" end
# File lib/hashie/dash.rb, line 188 def initialize_attributes(attributes) return unless attributes cleaned_attributes = attributes.reject { |_attr, value| value.nil? } update_attributes(cleaned_attributes) end
# File lib/hashie/dash.rb, line 230 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
# File lib/hashie/dash.rb, line 195 def update_attributes(attributes) return unless attributes attributes.each_pair do |att, value| self[att] = value end end