aboutsummaryrefslogtreecommitdiffstats
path: root/activerecord/lib/active_record/store.rb
blob: b841b977fc8b9550a5f18fb0f5e825be4429a7f9 (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
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
require 'active_support/core_ext/hash/indifferent_access'

module ActiveRecord
  # Store gives you a thin wrapper around serialize for the purpose of storing hashes in a single column.
  # It's like a simple key/value store baked into your record when you don't care about being able to
  # query that store outside the context of a single record.
  #
  # You can then declare accessors to this store that are then accessible just like any other attribute
  # of the model. This is very helpful for easily exposing store keys to a form or elsewhere that's
  # already built around just accessing attributes on the model.
  #
  # Make sure that you declare the database column used for the serialized store as a text, so there's
  # plenty of room.
  #
  # You can set custom coder to encode/decode your serialized attributes to/from different formats.
  # JSON, YAML, Marshal are supported out of the box. Generally it can be any wrapper that provides +load+ and +dump+.
  #
  # Examples:
  #
  #   class User < ActiveRecord::Base
  #     store :settings, accessors: [ :color, :homepage ], coder: JSON
  #   end
  #
  #   u = User.new(color: 'black', homepage: '37signals.com')
  #   u.color                          # Accessor stored attribute
  #   u.settings[:country] = 'Denmark' # Any attribute, even if not specified with an accessor
  #
  #   # There is no difference between strings and symbols for accessing custom attributes
  #   u.settings[:country]  # => 'Denmark'
  #   u.settings['country'] # => 'Denmark'
  #
  #   # Add additional accessors to an existing store through store_accessor
  #   class SuperUser < User
  #     store_accessor :settings, :privileges, :servants
  #   end
  #
  # The stored attribute names can be retrieved using +stored_attributes+.
  #
  #   User.stored_attributes[:settings] # [:color, :homepage]
  #
  # == Overwriting default accessors
  #
  # All stored values are automatically available through accessors on the Active Record
  # object, but sometimes you want to specialize this behavior. This can be done by overwriting
  # the default accessors (using the same name as the attribute) and calling <tt>super</tt>
  # to actually change things.
  #
  #   class Song < ActiveRecord::Base
  #     # Uses a stored integer to hold the volume adjustment of the song
  #     store :settings, accessors: [:volume_adjustment]
  #
  #     def volume_adjustment=(decibels)
  #       super(decibels.to_i)
  #     end
  #
  #     def volume_adjustment
  #       super.to_i
  #     end
  #   end
  module Store
    extend ActiveSupport::Concern

    included do
      class_attribute :stored_attributes, instance_accessor: false
      self.stored_attributes = {}
    end

    module ClassMethods
      def store(store_attribute, options = {})
        serialize store_attribute, IndifferentCoder.new(options[:coder])
        store_accessor(store_attribute, options[:accessors]) if options.has_key? :accessors
      end

      def store_accessor(store_attribute, *keys)
        keys = keys.flatten

        _store_accessors_module.module_eval do
          keys.each do |key|
            define_method("#{key}=") do |value|
              write_store_attribute(store_attribute, key, value)
            end

            define_method(key) do
              read_store_attribute(store_attribute, key)
            end
          end
        end

        # assign new store attribute and create new hash to ensure that each class in the hierarchy
        # has its own hash of stored attributes.
        self.stored_attributes = {} if self.stored_attributes.blank?
        self.stored_attributes[store_attribute] ||= []
        self.stored_attributes[store_attribute] |= keys
      end

      def _store_accessors_module
        @_store_accessors_module ||= begin
          mod = Module.new
          include mod
          mod
        end
      end
    end

    protected
      def read_store_attribute(store_attribute, key)
        accessor = store_accessor_for(store_attribute)
        accessor.read(self, store_attribute, key)
      end

      def write_store_attribute(store_attribute, key, value)
        accessor = store_accessor_for(store_attribute)
        accessor.write(self, store_attribute, key, value)
      end

    private
      def store_accessor_for(store_attribute)
        @column_types[store_attribute.to_s].accessor
      end

      class HashAccessor
        def self.read(object, attribute, key)
          prepare(object, attribute)
          object.public_send(attribute)[key]
        end

        def self.write(object, attribute, key, value)
          prepare(object, attribute)
          if value != read(object, attribute, key)
            object.public_send :"#{attribute}_will_change!"
            object.public_send(attribute)[key] = value
          end
        end

        def self.prepare(object, attribute)
          object.public_send :"#{attribute}=", {} unless object.send(attribute)
        end
      end

      class StringKeyedHashAccessor < HashAccessor
        def self.read(object, attribute, key)
          super object, attribute, key.to_s
        end

        def self.write(object, attribute, key, value)
          super object, attribute, key.to_s, value
        end
      end

      class IndifferentHashAccessor < ActiveRecord::Store::HashAccessor
        def self.prepare(object, store_attribute)
          attribute = object.send(store_attribute)
          unless attribute.is_a?(ActiveSupport::HashWithIndifferentAccess)
            attribute = IndifferentCoder.as_indifferent_hash(attribute)
            object.send :"#{store_attribute}=", attribute
          end
          attribute
        end
      end

    class IndifferentCoder # :nodoc:
      def initialize(coder_or_class_name)
        @coder =
          if coder_or_class_name.respond_to?(:load) && coder_or_class_name.respond_to?(:dump)
            coder_or_class_name
          else
            ActiveRecord::Coders::YAMLColumn.new(coder_or_class_name || Object)
          end
      end

      def dump(obj)
        @coder.dump self.class.as_indifferent_hash(obj)
      end

      def load(yaml)
        self.class.as_indifferent_hash(@coder.load(yaml))
      end

      def self.as_indifferent_hash(obj)
        case obj
        when ActiveSupport::HashWithIndifferentAccess
          obj
        when Hash
          obj.with_indifferent_access
        else
          ActiveSupport::HashWithIndifferentAccess.new
        end
      end
    end
  end
end