aboutsummaryrefslogtreecommitdiffstats
path: root/activemodel/lib/active_model/dirty.rb
blob: a82ce1bee0766342a540b2e2682dd3b8b1d1f48d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
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
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
require 'active_model/attribute_methods'
require 'active_support/concern'
require 'active_support/hash_with_indifferent_access'
require 'active_support/core_ext/object/duplicable'

module ActiveModel
  # == Active Model Call Backs
  #
  # Provides a way to track changes in your object in the same way as 
  # Active Record does.
  # 
  # The requirements to implement ActiveModel::Dirty are to:
  #
  # * <tt>include ActiveModel::Dirty</tt> in your object
  # * Call <tt>define_attribute_methods</tt> passing each method you want to 
  #   track
  # * Call <tt>attr_name_will_change!</tt> before each change to the tracked 
  #   attribute
  # 
  # If you wish to also track previous changes on save or update, you need to 
  # add
  # 
  #   @previously_changed = changes
  # 
  # inside of your save or update method.
  # 
  # A minimal implementation could be:
  # 
  #   class Person
  #   
  #     include ActiveModel::Dirty
  #   
  #     define_attribute_methods [:name]
  #   
  #     def name
  #       @name
  #     end
  #   
  #     def name=(val)
  #       name_will_change!
  #       @name = val
  #     end
  #   
  #     def save
  #       @previously_changed = changes
  #     end
  #   
  #   end
  # 
  # == Examples:
  #
  # A newly instantiated object is unchanged:
  #   person = Person.find_by_name('Uncle Bob')
  #   person.changed?       # => false
  #
  # Change the name:
  #   person.name = 'Bob'
  #   person.changed?       # => true
  #   person.name_changed?  # => true
  #   person.name_was       # => 'Uncle Bob'
  #   person.name_change    # => ['Uncle Bob', 'Bob']
  #   person.name = 'Bill'
  #   person.name_change    # => ['Uncle Bob', 'Bill']
  #
  # Save the changes:
  #   person.save
  #   person.changed?       # => false
  #   person.name_changed?  # => false
  #
  # Assigning the same value leaves the attribute unchanged:
  #   person.name = 'Bill'
  #   person.name_changed?  # => false
  #   person.name_change    # => nil
  #
  # Which attributes have changed?
  #   person.name = 'Bob'
  #   person.changed        # => ['name']
  #   person.changes        # => { 'name' => ['Bill', 'Bob'] }
  #
  # Resetting an attribute returns it to its original state:
  #   person.reset_name!    # => 'Bill'
  #   person.changed?       # => false
  #   person.name_changed?  # => false
  #   person.name           # => 'Bill'
  #
  # Before modifying an attribute in-place:
  #   person.name_will_change!
  #   person.name << 'y'
  #   person.name_change    # => ['Bill', 'Billy']
  module Dirty
    extend ActiveSupport::Concern
    include ActiveModel::AttributeMethods

    included do
      attribute_method_suffix '_changed?', '_change', '_will_change!', '_was'
      attribute_method_affix :prefix => 'reset_', :suffix => '!'
    end

    # Do any attributes have unsaved changes?
    #   person.changed? # => false
    #   person.name = 'bob'
    #   person.changed? # => true
    def changed?
      !changed_attributes.empty?
    end

    # List of attributes with unsaved changes.
    #   person.changed # => []
    #   person.name = 'bob'
    #   person.changed # => ['name']
    def changed
      changed_attributes.keys
    end

    # Map of changed attrs => [original value, new value].
    #   person.changes # => {}
    #   person.name = 'bob'
    #   person.changes # => { 'name' => ['bill', 'bob'] }
    def changes
      changed.inject(HashWithIndifferentAccess.new){ |h, attr| h[attr] = attribute_change(attr); h }
    end

    # Map of attributes that were changed when the model was saved.
    #   person.name # => 'bob'
    #   person.name = 'robert'
    #   person.save
    #   person.previous_changes # => {'name' => ['bob, 'robert']}
    def previous_changes
      @previously_changed
    end

    # Map of change <tt>attr => original value</tt>.
    def changed_attributes
      @changed_attributes ||= {}
    end

    private

      # Handle <tt>*_changed?</tt> for +method_missing+.
      def attribute_changed?(attr)
        changed_attributes.include?(attr)
      end

      # Handle <tt>*_change</tt> for +method_missing+.
      def attribute_change(attr)
        [changed_attributes[attr], __send__(attr)] if attribute_changed?(attr)
      end

      # Handle <tt>*_was</tt> for +method_missing+.
      def attribute_was(attr)
        attribute_changed?(attr) ? changed_attributes[attr] : __send__(attr)
      end

      # Handle <tt>*_will_change!</tt> for +method_missing+.
      def attribute_will_change!(attr)
        begin
          value = __send__(attr)
          value = value.duplicable? ? value.clone : value
        rescue TypeError, NoMethodError
        end

        changed_attributes[attr] = value
      end

      # Handle <tt>reset_*!</tt> for +method_missing+.
      def reset_attribute!(attr)
        __send__("#{attr}=", changed_attributes[attr]) if attribute_changed?(attr)
      end
  end
end