aboutsummaryrefslogtreecommitdiffstats
path: root/activesupport/lib/active_support/new_callbacks.rb
blob: 56b510d52eda7d00830b53e98377c3e2d4f8e6fe (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
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
require 'active_support/core_ext/array/wrap'
require 'active_support/core_ext/class/inheritable_attributes'

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 :save
  #   end
  #
  #   class ConfigStorage < Storage
  #     save_callback :before, :saving_message
  #     def saving_message
  #       puts "saving..."
  #     end
  #
  #     save_callback :after do |object|
  #       puts "saved"
  #     end
  #
  #     def save
  #       _run_save_callbacks 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
  #
  #     save_callback :before, :prepare
  #     def prepare
  #       puts "preparing save"
  #     end
  #   end
  #
  #   class ConfigStorage < Storage
  #     save_callback :before, :saving_message
  #     def saving_message
  #       puts "saving..."
  #     end
  #
  #     save_callback :after do |object|
  #       puts "saved"
  #     end
  #
  #     def save
  #       _run_save_callbacks do
  #         puts "- save"
  #       end
  #     end
  #   end
  #
  #   config = ConfigStorage.new
  #   config.save
  #
  # Output:
  #   preparing save
  #   saving...
  #   - save
  #   saved
  module NewCallbacks
    def self.included(klass)
      klass.extend ClassMethods
    end
        
    def run_callbacks(kind, options = {}, &blk)
      send("_run_#{kind}_callbacks", &blk)
    end
    
    class Callback
      @@_callback_sequence = 0
      
      attr_accessor :filter, :kind, :name, :options, :per_key, :klass
      def initialize(filter, kind, options, klass)
        @kind, @klass = 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(klass)
        obj                  = super()
        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 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, options = {})
        object, terminator = (options || {}).values_at(:object, :terminator)
        
        return if key && !object.send("_one_time_conditions_valid_#{@callback_id}?")
        
        terminator ||= false
        
        # 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 = (#{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}"
            txt, line = <<-RUBY_EVAL, __LINE__ + 1
              def #{name}(halted)
                #{@compiled_options[0] || "if true"} && !halted
                  #{@filter} do
                    yield self
                  end
                else
                  yield self
                end
              end
            RUBY_EVAL
            @klass.class_eval(txt, __FILE__, line)
            "#{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, options = {})
        object = (options || {})[:object]
        
        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)

          @klass.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
            def #{method_name}(&blk)
              #{method_name}_object.send(:#{kind}, 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.metaclass.class_eval(
            "def #{kind}(context, &block) filter(context, &block) end",
            __FILE__, __LINE__ - 1)
        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
      def initialize(symbol)
        @symbol = symbol
      end
      
      def compile(key = nil, options = {})
        method = []
        method << "halted = false"
        each do |callback|
          method << callback.start(key, options)
        end
        method << "yield self if block_given? && !halted"
        reverse_each do |callback|
          method << callback.end(key, options)
        end
        method.compact.join("\n")
      end
      
      def clone(klass)
        chain = CallbackChain.new(@symbol)
        chain.push(*map {|c| c.clone(klass)})
      end
    end
        
    module ClassMethods
      CHAINS = {:before => :before, :around => :before, :after => :after}
      
      # Make the _run_save_callbacks 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_save_callbacks do
      #   save
      # end
      #
      # The _run_save_callbacks 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)
        body = send("_#{symbol}_callbacks").
          compile(nil, :terminator => send("_#{symbol}_terminator"))

        body, line = <<-RUBY_EVAL, __LINE__
          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
        RUBY_EVAL
  
        undef_method "_run_#{symbol}_callbacks" if method_defined?("_run_#{symbol}_callbacks")
        class_eval body, __FILE__, line
      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, obj, &blk)
        @_keyed_callbacks ||= {}
        @_keyed_callbacks[name] ||= begin
          str = send("_#{kind}_callbacks").
            compile(name, :object => obj, :terminator => send("_#{kind}_terminator"))

          class_eval "def #{name}() #{str} end", __FILE__, __LINE__
                    
          true
        end
      end
      
      # Define callbacks.
      #
      # Creates a <name>_callback method that you can use to add callbacks.
      #
      # Syntax:
      #   save_callback :before, :before_meth
      #   save_callback :after,  :after_meth, :if => :condition
      #   save_callback :around {|r| stuff; yield; stuff }
      #
      # The <name>_callback method also updates the _run_<name>_callbacks
      # method, which is the public API to run the callbacks.
      #
      # Also creates a skip_<name>_callback method that you can use to skip
      # callbacks.
      #
      # When creating or skipping callbacks, you can specify conditions that
      # are always the same for a given key. For instance, in ActionPack,
      # 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_dispatch_callbacks(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 _update_callbacks(name, filters = CallbackChain.new(name), block = nil)
        type = [:before, :after, :around].include?(filters.first) ? filters.shift : :before
        options = filters.last.is_a?(Hash) ? filters.pop : {}
        filters.unshift(block) if block

        callbacks = send("_#{name}_callbacks")
        yield callbacks, type, filters, options if block_given?

        _define_runner(name)
      end

      alias_method :_reset_callbacks, :_update_callbacks

      def set_callback(name, *filters, &block)
        _update_callbacks(name, filters, block) do |callbacks, type, filters, options|        
          filters.map! do |filter|
            # overrides parent class
            callbacks.delete_if {|c| c.matches?(type, filter) }
            Callback.new(filter, type, options.dup, self)
          end

          options[:prepend] ? callbacks.unshift(*filters) : callbacks.push(*filters)
        end
      end

      def skip_callback(name, *filters, &block)
        _update_callbacks(name, filters, block) do |callbacks, type, filters, options|
          filters.each do |filter|
            callbacks = send("_#{name}_callbacks=", callbacks.clone(self))

            filter = callbacks.find {|c| c.matches?(type, filter) }

            if filter && options.any?
              filter.recompile!(options, options[:per_key] || {})
            else
              callbacks.delete(filter)
            end
          end
        end
      end

      def define_callbacks(*symbols)
        terminator = symbols.pop if symbols.last.is_a?(String)
        symbols.each do |symbol|
          extlib_inheritable_accessor("_#{symbol}_terminator") { terminator }

          extlib_inheritable_accessor("_#{symbol}_callbacks") do
            CallbackChain.new(symbol)
          end

          _define_runner(symbol)
        end
      end
    end
  end
end