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
|
module ActiveRecord
ActiveSupport.on_load(:active_record_config) do
# Determine whether to store the full constant name including namespace when using STI
mattr_accessor :store_full_sti_class, instance_accessor: false
self.store_full_sti_class = true
end
module Inheritance
extend ActiveSupport::Concern
included do
config_attribute :store_full_sti_class
end
module ClassMethods
# True if this isn't a concrete subclass needing a STI type condition.
def descends_from_active_record?
sup = active_record_super
if sup.abstract_class?
sup.descends_from_active_record?
elsif self == Base
false
else
[Base, Model].include?(sup) || !columns_hash.include?(inheritance_column)
end
end
def finder_needs_type_condition? #:nodoc:
# This is like this because benchmarking justifies the strange :false stuff
:true == (@finder_needs_type_condition ||= descends_from_active_record? ? :false : :true)
end
def symbolized_base_class
@symbolized_base_class ||= base_class.to_s.to_sym
end
def symbolized_sti_name
@symbolized_sti_name ||= sti_name.present? ? sti_name.to_sym : symbolized_base_class
end
# Returns the class descending directly from ActiveRecord::Base (or
# that includes ActiveRecord::Model), or an abstract class, if any, in
# the inheritance hierarchy.
#
# If A extends AR::Base, A.base_class will return A. If B descends from A
# through some arbitrarily deep hierarchy, B.base_class will return A.
#
# If B < A and C < B and if A is an abstract_class then both B.base_class
# and C.base_class would return B as the answer since A is an abstract_class.
def base_class
unless self < ActiveRecord::Tag
raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
end
sup = active_record_super
if sup == Base || sup == Model || sup.abstract_class?
self
else
sup.base_class
end
end
# Set this to true if this is an abstract class (see <tt>abstract_class?</tt>).
# If you are using inheritance with ActiveRecord and don't want child classes
# to utilize the implied STI table name of the parent class, this will need to be true.
# For example, given the following:
#
# class SuperClass < ActiveRecord::Base
# self.abstract_class = true
# end
# class Child < SuperClass
# self.table_name = 'the_table_i_really_want'
# end
#
#
# <tt>self.abstract_class = true</tt> is required to make <tt>Child<.find,.create, or any Arel method></tt> use <tt>the_table_i_really_want</tt> instead of a table called <tt>super_classes</tt>
#
attr_accessor :abstract_class
# Returns whether this class is an abstract class or not.
def abstract_class?
defined?(@abstract_class) && @abstract_class == true
end
def sti_name
store_full_sti_class ? name : name.demodulize
end
# Finder methods must instantiate through this method to work with the
# single-table inheritance model that makes it possible to create
# objects of different types from the same table.
def instantiate(record, column_types = {})
sti_class = find_sti_class(record[inheritance_column])
column_types = sti_class.decorate_columns(column_types)
sti_class.allocate.init_with('attributes' => record, 'column_types' => column_types)
end
# For internal use.
#
# If this class includes ActiveRecord::Model then it won't have a
# superclass. So this provides a way to get to the 'root' (ActiveRecord::Model).
def active_record_super #:nodoc:
superclass < Model ? superclass : Model
end
protected
# Returns the class type of the record using the current module as a prefix. So descendants of
# MyApp::Business::Account would appear as MyApp::Business::AccountSubclass.
def compute_type(type_name)
if type_name.match(/^::/)
# If the type is prefixed with a scope operator then we assume that
# the type_name is an absolute reference.
ActiveSupport::Dependencies.constantize(type_name)
else
# Build a list of candidates to search for
candidates = []
name.scan(/::|$/) { candidates.unshift "#{$`}::#{type_name}" }
candidates << type_name
candidates.each do |candidate|
begin
constant = ActiveSupport::Dependencies.constantize(candidate)
return constant if candidate == constant.to_s
rescue NameError => e
# We don't want to swallow NoMethodError < NameError errors
raise e unless e.instance_of?(NameError)
end
end
raise NameError, "uninitialized constant #{candidates.first}"
end
end
private
def find_sti_class(type_name)
if type_name.blank? || !columns_hash.include?(inheritance_column)
self
else
begin
if store_full_sti_class
ActiveSupport::Dependencies.constantize(type_name)
else
compute_type(type_name)
end
rescue NameError
raise SubclassNotFound,
"The single-table inheritance mechanism failed to locate the subclass: '#{type_name}'. " +
"This error is raised because the column '#{inheritance_column}' is reserved for storing the class in case of inheritance. " +
"Please rename this column if you didn't intend it to be used for storing the inheritance class " +
"or overwrite #{name}.inheritance_column to use another column for that information."
end
end
end
def type_condition(table = arel_table)
sti_column = table[inheritance_column.to_sym]
sti_names = ([self] + descendants).map { |model| model.sti_name }
sti_column.in(sti_names)
end
end
private
# Sets the attribute used for single table inheritance to this class name if this is not the
# ActiveRecord::Base descendant.
# Considering the hierarchy Reply < Message < ActiveRecord::Base, this makes it possible to
# do Reply.new without having to set <tt>Reply[Reply.inheritance_column] = "Reply"</tt> yourself.
# No such attribute would be set for objects of the Message class in that example.
def ensure_proper_type
klass = self.class
if klass.finder_needs_type_condition?
write_attribute(klass.inheritance_column, klass.sti_name)
end
end
end
end
|
