Class: Hashie::Dash

Inherits:
Hash
  • Object
show all
Includes:
PrettyInspect
Defined in:
lib/hashie/dash.rb

Overview

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.

Direct Known Subclasses

Trash

Class Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from PrettyInspect

#hashie_inspect, included

Methods inherited from Hash

#to_hash, #to_json

Methods included from HashExtensions

#hashie_stringify_keys, #hashie_stringify_keys!, included, #to_mash

Constructor Details

#initialize(attributes = {}, &block) ⇒ Dash

You may initialize a Dash with an attributes hash just like you would many other kinds of data objects.



75
76
77
78
79
80
81
82
83
84
85
 
# File 'lib/hashie/dash.rb', line 75

def initialize(attributes = {}, &block)
  super(&block)

  self.class.defaults.each_pair do |prop, value|
    self[prop] = value
  end

  attributes.each_pair do |att, value|
    self[att] = value
  end if attributes
end

Class Attribute Details

.defaults ⇒ Object (readonly)

Returns the value of attribute defaults.



55
56
57
 
# File 'lib/hashie/dash.rb', line 55

def defaults
  @defaults
end

.properties ⇒ Object (readonly)

Returns the value of attribute properties.



55
56
57
 
# File 'lib/hashie/dash.rb', line 55

def properties
  @properties
end

Class Method Details

.inherited(klass) ⇒ Object 



60
61
62
63
64
65
 
# File 'lib/hashie/dash.rb', line 60

def self.inherited(klass)
  super
  (@subclasses ||= Set.new) << klass
  klass.instance_variable_set('@properties', self.properties.dup)
  klass.instance_variable_set('@defaults', self.defaults.dup)
end

.property(property_name, options = {}) ⇒ Object

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.



26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
 
# File 'lib/hashie/dash.rb', line 26

def self.property(property_name, options = {})
  property_name = property_name.to_sym

  self.properties << property_name

  if options.has_key?(:default)
    self.defaults[property_name] = options[:default] 
  elsif self.defaults.has_key?(property_name)
    self.defaults.delete property_name
  end

  unless instance_methods.map { |m| m.to_s }.include?("#{property_name}=")
    class_eval <<-ACCESSORS
      def #{property_name}(&block)
        self.[](#{property_name.to_s.inspect}, &block)
      end

      def #{property_name}=(value)
        self.[]=(#{property_name.to_s.inspect}, value)
      end
    ACCESSORS
  end

  if defined? @subclasses
    @subclasses.each { |klass| klass.property(property_name, options) }
  end
end

.property?(name) ⇒ Boolean

Check to see if the specified property has already been defined.

Returns:

  • (Boolean) 


69
70
71
 
# File 'lib/hashie/dash.rb', line 69

def self.property?(name)
  properties.include? name.to_sym
end

Instance Method Details

#[](property) {|value| ... } ⇒ Object

Retrieve a value from the Dash (will return the property’s default value if it hasn’t been set).

Yields:

  • (value) 


93
94
95
96
97
98
 
# File 'lib/hashie/dash.rb', line 93

def [](property)
  assert_property_exists! property
  value = super(property.to_s)
  yield value if block_given?
  value
end

#[]=(property, value) ⇒ Object

Set a value on the Dash in a Hash-like way. Only works on pre-existing properties.



102
103
104
105
 
# File 'lib/hashie/dash.rb', line 102

def []=(property, value)
  assert_property_exists! property
  super(property.to_s, value)
end