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
192
193
194
195
196
197
198
|
require 'active_support/core_ext/object/deep_dup'
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:
#
# Conversation.active
# Conversation.archived
#
# 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])
#
# Where conditions on an enum attribute must use the ordinal value of an enum.
module Enum
def self.extended(base) # :nodoc:
base.class_attribute(:defined_enums)
base.defined_enums = {}
end
def inherited(base) # :nodoc:
base.defined_enums = defined_enums.deep_dup
super
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
detect_enum_conflict!(name, name.to_s.pluralize, true)
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
klass.send(:detect_enum_conflict!, name, "#{name}=")
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
klass.send(:detect_enum_conflict!, name, name)
define_method(name) { enum_values.key self[name] }
# def status_before_type_cast() statuses.key self[:status] end
klass.send(:detect_enum_conflict!, name, "#{name}_before_type_cast")
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
# def active?() status == 0 end
klass.send(:detect_enum_conflict!, name, "#{value}?")
define_method("#{value}?") { self[name] == i }
# def active!() update! status: :active end
klass.send(:detect_enum_conflict!, name, "#{value}!")
define_method("#{value}!") { update! name => value }
# scope :active, -> { where status: 0 }
klass.send(:detect_enum_conflict!, name, value, true)
klass.scope value, -> { klass.where name => i }
end
end
defined_enums[name.to_s] = enum_values
end
end
private
def _enum_methods_module
@_enum_methods_module ||= begin
mod = Module.new do
private
def save_changed_attribute(attr_name, old)
if (mapping = self.class.defined_enums[attr_name.to_s])
value = read_attribute(attr_name)
if attribute_changed?(attr_name)
if mapping[old] == value
changed_attributes.delete(attr_name)
end
else
if old != value
changed_attributes[attr_name] = mapping.key old
end
end
else
super
end
end
end
include mod
mod
end
end
ENUM_CONFLICT_MESSAGE = \
"You tried to define an enum named \"%{enum}\" on the model \"%{klass}\", but " \
"this will generate a %{type} method \"%{method}\", which is already defined " \
"by %{source}."
def detect_enum_conflict!(enum_name, method_name, klass_method = false)
if klass_method && dangerous_class_method?(method_name)
raise ArgumentError, ENUM_CONFLICT_MESSAGE % {
enum: enum_name,
klass: self.name,
type: 'class',
method: method_name,
source: 'Active Record'
}
elsif !klass_method && dangerous_attribute_method?(method_name)
raise ArgumentError, ENUM_CONFLICT_MESSAGE % {
enum: enum_name,
klass: self.name,
type: 'instance',
method: method_name,
source: 'Active Record'
}
elsif !klass_method && method_defined_within?(method_name, _enum_methods_module, Module)
raise ArgumentError, ENUM_CONFLICT_MESSAGE % {
enum: enum_name,
klass: self.name,
type: 'instance',
method: method_name,
source: 'another enum'
}
end
end
end
end
|
