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
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
|
require 'active_support/descendants_tracker'
require 'active_support/core_ext/array/wrap'
require 'active_support/core_ext/class/inheritable_attributes'
require 'active_support/core_ext/kernel/reporting'
require 'active_support/core_ext/kernel/singleton_class'
module ActiveSupport
# Callbacks are hooks into the life cycle 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 :save
# end
#
# class ConfigStorage < Storage
# set_callback :save, :before, :saving_message
# def saving_message
# puts "saving..."
# end
#
# set_callback :save, :after do |object|
# puts "saved"
# end
#
# def save
# run_callbacks :save do
# puts "- save"
# end
# 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 :save
#
# set_callback :save, :before, :prepare
# def prepare
# puts "preparing save"
# end
# end
#
# class ConfigStorage < Storage
# set_callback :save, :before, :saving_message
# def saving_message
# puts "saving..."
# end
#
# set_callback :save, :after do |object|
# puts "saved"
# end
#
# def save
# run_callbacks :save do
# puts "- save"
# end
# end
# end
#
# config = ConfigStorage.new
# config.save
#
# Output:
# preparing save
# saving...
# - save
# saved
#
module Callbacks
extend Concern
included do
extend ActiveSupport::DescendantsTracker
end
def run_callbacks(kind, *args, &block)
send("_run_#{kind}_callbacks", *args, &block)
end
class Callback
@@_callback_sequence = 0
attr_accessor :chain, :filter, :kind, :options, :per_key, :klass, :raw_filter
def initialize(chain, filter, kind, options, klass)
@chain, @kind, @klass = chain, kind, klass
normalize_options!(options)
@per_key = options.delete(:per_key)
@raw_filter, @options = filter, options
@filter = _compile_filter(filter)
@compiled_options = _compile_options(options)
@callback_id = next_id
_compile_per_key_options
end
def clone(chain, klass)
obj = super()
obj.chain = chain
obj.klass = klass
obj.per_key = @per_key.dup
obj.options = @options.dup
obj.per_key[:if] = @per_key[:if].dup
obj.per_key[:unless] = @per_key[:unless].dup
obj.options[:if] = @options[:if].dup
obj.options[:unless] = @options[:unless].dup
obj
end
def normalize_options!(options)
options[:if] = Array.wrap(options[:if])
options[:unless] = Array.wrap(options[:unless])
options[:per_key] ||= {}
options[:per_key][:if] = Array.wrap(options[:per_key][:if])
options[:per_key][:unless] = Array.wrap(options[:per_key][:unless])
end
def name
chain.name
end
def next_id
@@_callback_sequence += 1
end
def matches?(_kind, _filter)
@kind == _kind && @filter == _filter
end
def _update_filter(filter_options, new_options)
filter_options[:if].push(new_options[:unless]) if new_options.key?(:unless)
filter_options[:unless].push(new_options[:if]) if new_options.key?(:if)
end
def recompile!(_options, _per_key)
_update_filter(self.options, _options)
_update_filter(self.per_key, _per_key)
@callback_id = next_id
@filter = _compile_filter(@raw_filter)
@compiled_options = _compile_options(@options)
_compile_per_key_options
end
def _compile_per_key_options
key_options = _compile_options(@per_key)
@klass.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
def _one_time_conditions_valid_#{@callback_id}?
true #{key_options[0]}
end
RUBY_EVAL
end
# This will supply contents for before and around filters, and no
# contents for after filters (for the forward pass).
def start(key=nil, object=nil)
return if key && !object.send("_one_time_conditions_valid_#{@callback_id}?")
# options[0] is the compiled form of supplied conditions
# options[1] is the "end" for the conditional
#
if @kind == :before || @kind == :around
if @kind == :before
# if condition # before_save :filter_name, :if => :condition
# filter_name
# end
filter = <<-RUBY_EVAL
unless halted
result = #{@filter}
halted = (#{chain.config[:terminator]})
end
RUBY_EVAL
[@compiled_options[0], filter, @compiled_options[1]].compact.join("\n")
else
# Compile around filters with conditions into proxy methods
# that contain the conditions.
#
# For `around_save :filter_name, :if => :condition':
#
# def _conditional_callback_save_17
# if condition
# filter_name do
# yield self
# end
# else
# yield self
# end
# end
#
name = "_conditional_callback_#{@kind}_#{next_id}"
@klass.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
def #{name}(halted)
#{@compiled_options[0] || "if true"} && !halted
#{@filter} do
yield self
end
else
yield self
end
end
RUBY_EVAL
"#{name}(halted) do"
end
end
end
# This will supply contents for around and after filters, but not
# before filters (for the backward pass).
def end(key=nil, object=nil)
return if key && !object.send("_one_time_conditions_valid_#{@callback_id}?")
if @kind == :around || @kind == :after
# if condition # after_save :filter_name, :if => :condition
# filter_name
# end
if @kind == :after
[@compiled_options[0], @filter, @compiled_options[1]].compact.join("\n")
else
"end"
end
end
end
private
# Options support the same options as filters themselves (and support
# symbols, string, procs, and objects), so compile a conditional
# expression based on the options
def _compile_options(options)
return [] if options[:if].empty? && options[:unless].empty?
conditions = []
unless options[:if].empty?
conditions << Array.wrap(_compile_filter(options[:if]))
end
unless options[:unless].empty?
conditions << Array.wrap(_compile_filter(options[:unless])).map {|f| "!#{f}"}
end
["if #{conditions.flatten.join(" && ")}", "end"]
end
# Filters support:
#
# Arrays:: Used in conditions. This is used to specify
# multiple conditions. Used internally to
# merge conditions from skip_* filters
# Symbols:: A method to call
# Strings:: Some content to evaluate
# Procs:: A proc to call with the object
# Objects:: An object with a before_foo method on it to call
#
# All of these objects are compiled into methods and handled
# the same after this point:
#
# Arrays:: Merged together into a single filter
# Symbols:: Already methods
# Strings:: class_eval'ed into methods
# Procs:: define_method'ed into methods
# Objects::
# a method is created that calls the before_foo method
# on the object.
#
def _compile_filter(filter)
method_name = "_callback_#{@kind}_#{next_id}"
case filter
when Array
filter.map {|f| _compile_filter(f)}
when Symbol
filter
when String
"(#{filter})"
when Proc
@klass.send(:define_method, method_name, &filter)
return method_name if filter.arity <= 0
method_name << (filter.arity == 1 ? "(self)" : " self, Proc.new ")
else
@klass.send(:define_method, "#{method_name}_object") { filter }
_normalize_legacy_filter(kind, filter)
scopes = Array.wrap(chain.config[:scope])
method_to_call = scopes.map{ |s| s.is_a?(Symbol) ? send(s) : s }.join("_")
@klass.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
def #{method_name}(&blk)
#{method_name}_object.send(:#{method_to_call}, self, &blk)
end
RUBY_EVAL
method_name
end
end
def _normalize_legacy_filter(kind, filter)
if !filter.respond_to?(kind) && filter.respond_to?(:filter)
filter.singleton_class.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
def #{kind}(context, &block) filter(context, &block) end
RUBY_EVAL
elsif filter.respond_to?(:before) && filter.respond_to?(:after) && kind == :around
def filter.around(context)
should_continue = before(context)
yield if should_continue
after(context)
end
end
end
end
# An Array with a compile method
class CallbackChain < Array
attr_reader :name, :config
def initialize(name, config)
@name = name
@config = {
:terminator => "false",
:rescuable => false,
:scope => [ :kind ]
}.merge(config)
end
def compile(key=nil, object=nil)
method = []
method << "value = nil"
method << "halted = false"
each do |callback|
method << callback.start(key, object)
end
if config[:rescuable]
method << "rescued_error = nil"
method << "begin"
end
method << "value = yield if block_given? && !halted"
if config[:rescuable]
method << "rescue Exception => e"
method << "rescued_error = e"
method << "end"
end
reverse_each do |callback|
method << callback.end(key, object)
end
method << "raise rescued_error if rescued_error" if config[:rescuable]
method << "halted ? false : (block_given? ? value : true)"
method.compact.join("\n")
end
end
module ClassMethods
# Make the run_callbacks :save method. The generated method takes
# a block that it'll yield to. It'll call the before and around filters
# in order, yield the block, and then run the after filters.
#
# run_callbacks :save do
# save
# end
#
# The run_callbacks :save method can optionally take a key, which
# will be used to compile an optimized callback method for each
# key. See #define_callbacks for more information.
#
def __define_runner(symbol) #:nodoc:
body = send("_#{symbol}_callbacks").compile(nil)
silence_warnings do
undef_method "_run_#{symbol}_callbacks" if method_defined?("_run_#{symbol}_callbacks")
class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
def _run_#{symbol}_callbacks(key = nil, &blk)
if key
name = "_run__\#{self.class.name.hash.abs}__#{symbol}__\#{key.hash.abs}__callbacks"
unless respond_to?(name)
self.class.__create_keyed_callback(name, :#{symbol}, self, &blk)
end
send(name, &blk)
else
#{body}
end
end
private :_run_#{symbol}_callbacks
RUBY_EVAL
end
end
# This is called the first time a callback is called with a particular
# key. It creates a new callback method for the key, calculating
# which callbacks can be omitted because of per_key conditions.
#
def __create_keyed_callback(name, kind, object, &blk) #:nodoc:
@_keyed_callbacks ||= {}
@_keyed_callbacks[name] ||= begin
str = send("_#{kind}_callbacks").compile(name, object)
class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
def #{name}() #{str} end
protected :#{name}
RUBY_EVAL
true
end
end
# This is used internally to append, prepend and skip callbacks to the
# CallbackChain.
#
def __update_callbacks(name, filters = [], block = nil) #:nodoc:
type = [:before, :after, :around].include?(filters.first) ? filters.shift : :before
options = filters.last.is_a?(Hash) ? filters.pop : {}
filters.unshift(block) if block
([self] + ActiveSupport::DescendantsTracker.descendants(self)).each do |target|
chain = target.send("_#{name}_callbacks")
yield chain, type, filters, options
target.__define_runner(name)
end
end
# Set callbacks for a previously defined callback.
#
# Syntax:
# set_callback :save, :before, :before_meth
# set_callback :save, :after, :after_meth, :if => :condition
# set_callback :save, :around, lambda { |r| stuff; yield; stuff }
#
# Use skip_callback to skip any defined one.
#
# When creating or skipping callbacks, you can specify conditions that
# are always the same for a given key. For instance, in Action Pack,
# we convert :only and :except conditions into per-key conditions.
#
# before_filter :authenticate, :except => "index"
#
# becomes
#
# dispatch_callback :before, :authenticate, :per_key => {:unless => proc {|c| c.action_name == "index"}}
#
# Per-Key conditions are evaluated only once per use of a given key.
# In the case of the above example, you would do:
#
# run_callbacks(:dispatch, action_name) { ... dispatch stuff ... }
#
# In that case, each action_name would get its own compiled callback
# method that took into consideration the per_key conditions. This
# is a speed improvement for ActionPack.
#
def set_callback(name, *filter_list, &block)
mapped = nil
__update_callbacks(name, filter_list, block) do |chain, type, filters, options|
mapped ||= filters.map do |filter|
Callback.new(chain, filter, type, options.dup, self)
end
filters.each do |filter|
chain.delete_if {|c| c.matches?(type, filter) }
end
options[:prepend] ? chain.unshift(*(mapped.reverse)) : chain.push(*mapped)
end
end
# Skip a previously defined callback.
#
# class Writer < Person
# skip_callback :validate, :before, :check_membership, :if => lambda { self.age > 18 }
# end
#
def skip_callback(name, *filter_list, &block)
__update_callbacks(name, filter_list, block) do |chain, type, filters, options|
filters.each do |filter|
filter = chain.find {|c| c.matches?(type, filter) }
if filter && options.any?
new_filter = filter.clone(chain, self)
chain.insert(chain.index(filter), new_filter)
new_filter.recompile!(options, options[:per_key] || {})
end
chain.delete(filter)
end
end
end
# Reset callbacks for a given type.
#
def reset_callbacks(symbol)
callbacks = send("_#{symbol}_callbacks")
ActiveSupport::DescendantsTracker.descendants(self).each do |target|
chain = target.send("_#{symbol}_callbacks")
callbacks.each { |c| chain.delete(c) }
target.__define_runner(symbol)
end
callbacks.clear
__define_runner(symbol)
end
# Defines callbacks types:
#
# define_callbacks :validate
#
# This macro accepts the following options:
#
# * <tt>:terminator</tt> - Indicates when a before filter is considered
# to halted. This is a string to be eval'ed and has the result of the
# very filter available in the <tt>result</tt> variable:
#
# define_callbacks :validate, :terminator => "result == false"
#
# In the example above, if any before validate callbacks returns +false+,
# other callbacks are not executed. Defaults to "false", meaning no value
# halts the chain.
#
# * <tt>:rescuable</tt> - By default, after filters are not executed if
# the given block or a before filter raises an error. Set this option to
# true to change this behavior.
#
# * <tt>:scope</tt> - Indicates which methods should be executed when a class
# is given as callback. Defaults to <tt>[:kind]</tt>.
#
# class Audit
# def before(caller)
# puts 'Audit: before is called'
# end
#
# def before_save(caller)
# puts 'Audit: before_save is called'
# end
# end
#
# class Account
# include ActiveSupport::Callbacks
#
# define_callbacks :save
# set_callback :save, :before, Audit.new
#
# def save
# run_callbacks :save do
# puts 'save in main'
# end
# end
# end
#
# In the above case whenever you save an account the method <tt>Audit#before</tt> will
# be called. On the other hand
#
# define_callbacks :save, :scope => [:kind, :name]
#
# would trigger <tt>Audit#before_save</tt> instead. That's constructed by calling
# <tt>"#{kind}_#{name}"</tt> on the given instance. In this case "kind" is "before" and
# "name" is "save". In this context ":kind" and ":name" have special meanings: ":kind"
# refers to the kind of callback (before/after/around) and ":name" refers to the
# method on which callbacks are being defined.
#
# A declaration like
#
# define_callbacks :save, :scope => [:name]
#
# would call <tt>Audit#save</tt>.
#
def define_callbacks(*callbacks)
config = callbacks.last.is_a?(Hash) ? callbacks.pop : {}
callbacks.each do |callback|
extlib_inheritable_reader("_#{callback}_callbacks") do
CallbackChain.new(callback, config)
end
__define_runner(callback)
end
end
end
end
end
|