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
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
|
module ActiveSupport
# Callbacks are hooks into the lifecycle of an object that allow you to trigger logic
# before or after an alteration of the object state.
#
# Mixing in this module allows you to define callbacks in your class.
#
# Example:
# class Storage
# include ActiveSupport::Callbacks
#
# define_callbacks :before_save, :after_save
# end
#
# class ConfigStorage < Storage
# before_save :saving_message
# def saving_message
# puts "saving..."
# end
#
# after_save do |object|
# puts "saved"
# end
#
# def save
# run_callbacks(:before_save)
# puts "- save"
# run_callbacks(:after_save)
# end
# end
#
# config = ConfigStorage.new
# config.save
#
# Output:
# saving...
# - save
# saved
#
# Callbacks from parent classes are inherited.
#
# Example:
# class Storage
# include ActiveSupport::Callbacks
#
# define_callbacks :before_save, :after_save
#
# before_save :prepare
# def prepare
# puts "preparing save"
# end
# end
#
# class ConfigStorage < Storage
# before_save :saving_message
# def saving_message
# puts "saving..."
# end
#
# after_save do |object|
# puts "saved"
# end
#
# def save
# run_callbacks(:before_save)
# puts "- save"
# run_callbacks(:after_save)
# end
# end
#
# config = ConfigStorage.new
# config.save
#
# Output:
# preparing save
# saving...
# - save
# saved
module Callbacks
class Callback
def self.run(callbacks, object, options = {}, &terminator)
enumerator = options[:enumerator] || :each
unless block_given?
callbacks.send(enumerator) { |callback| callback.call(object) }
else
callbacks.send(enumerator) do |callback|
result = callback.call(object)
break result if terminator.call(result, object)
end
end
end
attr_reader :kind, :method, :identifier, :options
def initialize(kind, method, options = {})
@kind = kind
@method = method
@identifier = options[:identifier]
@options = options
end
def call(object)
evaluate_method(method, object) if should_run_callback?(object)
end
private
def evaluate_method(method, object)
case method
when Symbol
object.send(method)
when String
eval(method, object.instance_eval { binding })
when Proc, Method
method.call(object)
else
if method.respond_to?(kind)
method.send(kind, object)
else
raise ArgumentError,
"Callbacks must be a symbol denoting the method to call, a string to be evaluated, " +
"a block to be invoked, or an object responding to the callback method."
end
end
end
def should_run_callback?(object)
if options[:if]
evaluate_method(options[:if], object)
elsif options[:unless]
!evaluate_method(options[:unless], object)
else
true
end
end
end
def self.included(base)
base.extend ClassMethods
end
module ClassMethods
def define_callbacks(*callbacks)
callbacks.each do |callback|
class_eval <<-"end_eval"
def self.#{callback}(*methods, &block)
options = methods.extract_options!
methods << block if block_given?
callbacks = methods.map { |method| Callback.new(:#{callback}, method, options) }
(@#{callback}_callbacks ||= []).concat callbacks
end
def self.#{callback}_callback_chain
@#{callback}_callbacks ||= []
if superclass.respond_to?(:#{callback}_callback_chain)
superclass.#{callback}_callback_chain + @#{callback}_callbacks
else
@#{callback}_callbacks
end
end
end_eval
end
end
end
# Runs all the callbacks defined for the given options.
#
# If a block is given it will be called after each callback receiving as arguments:
#
# * the result from the callback
# * the object which has the callback
#
# If the result from the block evaluates to false, the callback chain is stopped.
#
# Example:
# class Storage
# include ActiveSupport::Callbacks
#
# define_callbacks :before_save, :after_save
# end
#
# class ConfigStorage < Storage
# before_save :pass
# before_save :pass
# before_save :stop
# before_save :pass
#
# def pass
# puts "pass"
# end
#
# def stop
# puts "stop"
# return false
# end
#
# def save
# result = run_callbacks(:before_save) { |result, object| result == false }
# puts "- save" if result
# end
# end
#
# config = ConfigStorage.new
# config.save
#
# Output:
# pass
# pass
# stop
def run_callbacks(kind, options = {}, &block)
Callback.run(self.class.send("#{kind}_callback_chain"), self, options, &block)
end
end
end
|
