aboutsummaryrefslogtreecommitdiffstats
path: root/activerecord/lib/active_record/enum.rb
blob: 53dde5e5648638df6dd2aa60814d549d9fbe6d2b (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
module ActiveRecord
  # Declare an enum attribute where the values map to integers in the database,
  # but can be queried by name. Example:
  #
  #   class Conversation < ActiveRecord::Base
  #     enum status: [ :active, :archived ]
  #   end
  #
  #   # conversation.update! status: 0
  #   conversation.active!
  #   conversation.active? # => true
  #   conversation.status  # => "active"
  #
  #   # conversation.update! status: 1
  #   conversation.archived!
  #   conversation.archived? # => true
  #   conversation.status    # => "archived"
  #
  #   # conversation.update! status: 1
  #   conversation.status = "archived"
  #
  #   # conversation.update! status: nil
  #   conversation.status = nil
  #   conversation.status.nil? # => true
  #   conversation.status      # => nil
  #
  # Scopes based on the allowed values of the enum field will be provided
  # as well. With the above example, it will create an +active+ and +archived+
  # scope.
  #
  # You can set the default value from the database declaration, like:
  #
  #   create_table :conversations do |t|
  #     t.column :status, :integer, default: 0
  #   end
  #
  # Good practice is to let the first declared status be the default.
  #
  # Finally, it's also possible to explicitly map the relation between attribute and
  # database integer with a +Hash+:
  #
  #   class Conversation < ActiveRecord::Base
  #     enum status: { active: 0, archived: 1 }
  #   end
  #
  # Note that when an +Array+ is used, the implicit mapping from the values to database
  # integers is derived from the order the values appear in the array. In the example,
  # <tt>:active</tt> is mapped to +0+ as it's the first element, and <tt>:archived</tt>
  # is mapped to +1+. In general, the +i+-th element is mapped to <tt>i-1</tt> in the
  # database.
  #
  # Therefore, once a value is added to the enum array, its position in the array must
  # be maintained, and new values should only be added to the end of the array. To
  # remove unused values, the explicit +Hash+ syntax should be used.
  #
  # In rare circumstances you might need to access the mapping directly.
  # The mappings are exposed through a class method with the pluralized attribute
  # name:
  #
  #   Conversation.statuses # => { "active" => 0, "archived" => 1 }
  #
  # Use that class method when you need to know the ordinal value of an enum:
  #
  #   Conversation.where("status <> ?", Conversation.statuses[:archived])
  module Enum
    DEFINED_ENUMS = {} # :nodoc:

    def enum_mapping_for(attr_name) # :nodoc:
      DEFINED_ENUMS[attr_name.to_s]
    end

    def enum(definitions)
      klass = self
      definitions.each do |name, values|
        # statuses = { }
        enum_values = ActiveSupport::HashWithIndifferentAccess.new
        name        = name.to_sym

        # def self.statuses statuses end
        klass.singleton_class.send(:define_method, name.to_s.pluralize) { enum_values }

        _enum_methods_module.module_eval do
          # def status=(value) self[:status] = statuses[value] end
          define_method("#{name}=") { |value|
            if enum_values.has_key?(value) || value.blank?
              self[name] = enum_values[value]
            elsif enum_values.has_value?(value)
              # Assigning a value directly is not a end-user feature, hence it's not documented.
              # This is used internally to make building objects from the generated scopes work
              # as expected, i.e. +Conversation.archived.build.archived?+ should be true.
              self[name] = value
            else
              raise ArgumentError, "'#{value}' is not a valid #{name}"
            end
          }

          # def status() statuses.key self[:status] end
          define_method(name) { enum_values.key self[name] }

          # def status_before_type_cast() statuses.key self[:status] end
          define_method("#{name}_before_type_cast") { enum_values.key self[name] }

          pairs = values.respond_to?(:each_pair) ? values.each_pair : values.each_with_index
          pairs.each do |value, i|
            enum_values[value] = i

            # scope :active, -> { where status: 0 }
            klass.scope value, -> { klass.where name => i }

            # def active?() status == 0 end
            define_method("#{value}?") { self[name] == i }

            # def active!() update! status: :active end
            define_method("#{value}!") { update! name => value }
          end

          DEFINED_ENUMS[name.to_s] = enum_values
        end
      end
    end

    private
      def _enum_methods_module
        @_enum_methods_module ||= begin
          mod = Module.new do
            private
              def save_changed_attribute(attr_name, value)
                if (mapping = self.class.enum_mapping_for(attr_name))
                  if attribute_changed?(attr_name)
                    old = changed_attributes[attr_name]

                    if mapping[old] == value
                      changed_attributes.delete(attr_name)
                    end
                  else
                    old = clone_attribute_value(:read_attribute, attr_name)

                    if old != value
                      changed_attributes[attr_name] = mapping.key old
                    end
                  end
                else
                  super
                end
              end
          end
          include mod
          mod
        end
      end
  end
end