require 'active_support/concern' require 'active_support/descendants_tracker' require 'active_support/core_ext/array/wrap' require 'active_support/core_ext/class/attribute' require 'active_support/core_ext/kernel/reporting' require 'active_support/core_ext/kernel/singleton_class' module ActiveSupport # \Callbacks are code hooks that are run at key points in an object's lifecycle. # The typical use case is to have a base class define a set of callbacks relevant # to the other functionality it supplies, so that subclasses can install callbacks # that enhance or modify the base functionality without needing to override # or redefine methods of the base class. # # Mixing in this module allows you to define the events in the object's lifecycle # that will support callbacks (via +ClassMethods.define_callbacks+), set the instance # methods, procs, or callback objects to be called (via +ClassMethods.set_callback+), # and run the installed callbacks at the appropriate times (via +run_callbacks+). # # Three kinds of callbacks are supported: before callbacks, run before a certain event; # after callbacks, run after the event; and around callbacks, blocks that surround the # event, triggering it when they yield. Callback code can be contained in instance # methods, procs or lambdas, or callback objects that respond to certain predetermined # methods. See +ClassMethods.set_callback+ for details. # # ==== Example # # class Record # include ActiveSupport::Callbacks # define_callbacks :save # # def save # run_callbacks :save do # puts "- save" # end # end # end # # class PersonRecord < Record # set_callback :save, :before, :saving_message # def saving_message # puts "saving..." # end # # set_callback :save, :after do |object| # puts "saved" # end # end # # person = PersonRecord.new # person.save # # Output: # saving... # - save # saved # module Callbacks extend Concern included do extend ActiveSupport::DescendantsTracker end # Runs the callbacks for the given event. # # Calls the before and around callbacks in the order they were set, yields # the block (if given one), and then runs the after callbacks in reverse order. # Optionally accepts a key, which will be used to compile an optimized callback # method for each key. See +ClassMethods.define_callbacks+ for more information. # # If the callback chain was halted, returns +false+. Otherwise returns the result # of the block, or +true+ if no block is given. # # run_callbacks :save do # save # end # def run_callbacks(kind, *args, &block) send("_run_#{kind}_callbacks", *args, &block) end class Callback #:nodoc:# @@_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 # case @kind when :before # if condition # before_save :filter_name, :if => :condition # filter_name # end filter = <<-RUBY_EVAL unless halted # This double assignment is to prevent warnings in 1.9.3. I would # remove the `result` variable, but apparently some other # generated code is depending on this variable being set sometimes # and sometimes not. result = result = #{@filter} halted = (#{chain.config[:terminator]}) end RUBY_EVAL [@compiled_options[0], filter, @compiled_options[1]].compact.join("\n") when :around # 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 # 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}?") case @kind when :after # if condition # after_save :filter_name, :if => :condition # filter_name # end [@compiled_options[0], @filter, @compiled_options[1]].compact.join("\n") when :around <<-RUBY_EVAL value end RUBY_EVAL 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 #:nodoc:# 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 # Generate the internal runner method called by +run_callbacks+. def __define_runner(symbol) #:nodoc: body = send("_#{symbol}_callbacks").compile 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)).reverse.each do |target| chain = target.send("_#{name}_callbacks") yield target, chain.dup, type, filters, options target.__define_runner(name) end end # Install a callback for the given event. # # set_callback :save, :before, :before_meth # set_callback :save, :after, :after_meth, :if => :condition # set_callback :save, :around, lambda { |r| stuff; result = yield; stuff } # # The second arguments indicates whether the callback is to be run +:before+, # +:after+, or +:around+ the event. If omitted, +:before+ is assumed. This # means the first example above can also be written as: # # set_callback :save, :before_meth # # The callback can specified as a symbol naming an instance method; as a proc, # lambda, or block; as a string to be instance evaluated; or as an object that # responds to a certain method determined by the :scope argument to # +define_callback+. # # If a proc, lambda, or block is given, its body is evaluated in the context # of the current object. It can also optionally accept the current object as # an argument. # # Before and around callbacks are called in the order that they are set; after # callbacks are called in the reverse order. # # Around callbacks can access the return value from the event, if it # wasn't halted, from the +yield+ call. # # ===== Options # # * :if - A symbol naming an instance method or a proc; the callback # will be called only when it returns a true value. # * :unless - A symbol naming an instance method or a proc; the callback # will be called only when it returns a false value. # * :prepend - If true, the callback will be prepended to the existing # chain rather than appended. # * :per_key - A hash with :if and :unless options; # see "Per-key conditions" below. # # ===== Per-key conditions # # 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 # # set_callback :process_action, :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(:process_action, 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 |target, 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) target.send("_#{name}_callbacks=", chain) end end # Skip a previously set callback. Like +set_callback+, :if or :unless # options may be passed in order to control when the callback is skipped. # # 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 |target, 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 target.send("_#{name}_callbacks=", chain) end end # Remove all set callbacks for the given event. # def reset_callbacks(symbol) callbacks = send("_#{symbol}_callbacks") ActiveSupport::DescendantsTracker.descendants(self).each do |target| chain = target.send("_#{symbol}_callbacks").dup callbacks.each { |c| chain.delete(c) } target.send("_#{symbol}_callbacks=", chain) target.__define_runner(symbol) end self.send("_#{symbol}_callbacks=", callbacks.dup.clear) __define_runner(symbol) end # Define sets of events in the object lifecycle that support callbacks. # # define_callbacks :validate # define_callbacks :initialize, :save, :destroy # # ===== Options # # * :terminator - Determines when a before filter will halt the callback # chain, preventing following callbacks from being called and the event from being # triggered. This is a string to be eval'ed. The result of the callback is available # in the result variable. # # define_callbacks :validate, :terminator => "result == false" # # In this example, if any before validate callbacks returns +false+, # other callbacks are not executed. Defaults to "false", meaning no value # halts the chain. # # * :rescuable - By default, after filters are not executed if # the given block or a before filter raises an error. By setting this option # to true exception raised by given block is stored and after # executing all the after callbacks the stored exception is raised. # # * :scope - Indicates which methods should be executed when an object # is used as a callback. # # 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 Audit#before will # be called. On the other hand # # define_callbacks :save, :scope => [:kind, :name] # # would trigger Audit#before_save instead. That's constructed by calling # #{kind}_#{name} 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 Audit#save. # def define_callbacks(*callbacks) config = callbacks.last.is_a?(Hash) ? callbacks.pop : {} callbacks.each do |callback| class_attribute "_#{callback}_callbacks" send("_#{callback}_callbacks=", CallbackChain.new(callback, config)) __define_runner(callback) end end end end end