require 'active_support/concern' require 'active_support/descendants_tracker' require 'active_support/core_ext/class/attribute' require 'active_support/core_ext/kernel/reporting' require 'active_support/core_ext/kernel/singleton_class' require 'active_support/core_ext/object/inclusion' 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. # # 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. # # 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, &block) runner_name = self.class.__define_callbacks(kind, self) send(runner_name, &block) end private # A hook invoked everytime a before callback is halted. # This can be overriden in AS::Callback implementors in order # to provide better debugging/logging. def halted_callback_hook(filter) end class Callback #:nodoc:# @@_callback_sequence = 0 attr_accessor :chain, :filter, :kind, :options, :klass, :raw_filter def initialize(chain, filter, kind, options, klass) @chain, @kind, @klass = chain, kind, klass deprecate_per_key_option(options) normalize_options!(options) @raw_filter, @options = filter, options @filter = _compile_filter(filter) recompile_options! end def deprecate_per_key_option(options) if options[:per_key] raise NotImplementedError, ":per_key option is no longer supported. Use generic :if and :unless options instead." end end def clone(chain, klass) obj = super() obj.chain = chain obj.klass = klass obj.options = @options.dup obj.options[:if] = @options[:if].dup obj.options[:unless] = @options[:unless].dup obj end def normalize_options!(options) options[:if] = Array(options[:if]) options[:unless] = Array(options[: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].concat(Array(new_options[:unless])) if new_options.key?(:unless) filter_options[:unless].concat(Array(new_options[:if])) if new_options.key?(:if) end def recompile!(_options) deprecate_per_key_option(_options) _update_filter(self.options, _options) recompile_options! end # Wraps code with filter def apply(code) case @kind when :before <<-RUBY_EVAL if !halted && #{@compiled_options} # This double assignment is to prevent warnings in 1.9.3 as # the `result` variable is not always used except if the # terminator code refers to it. result = result = #{@filter} halted = (#{chain.config[:terminator]}) if halted halted_callback_hook(#{@raw_filter.inspect.inspect}) end end #{code} RUBY_EVAL when :after <<-RUBY_EVAL #{code} if #{!chain.config[:skip_after_callbacks_if_terminated] || "!halted"} && #{@compiled_options} #{@filter} end RUBY_EVAL when :around name = define_conditional_callback <<-RUBY_EVAL #{name}(halted) do #{code} value end RUBY_EVAL end end private # Compile around filters with conditions into proxy methods # that contain the conditions. # # For `set_callback :save, :around, :filter_name, :if => :condition': # # def _conditional_callback_save_17 # if condition # filter_name do # yield self # end # else # yield self # end # end def define_conditional_callback name = "_conditional_callback_#{@kind}_#{next_id}" @klass.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1 def #{name}(halted) if #{@compiled_options} && !halted #{@filter} do yield self end else yield self end end RUBY_EVAL name end # 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 recompile_options! conditions = ["true"] unless options[:if].empty? conditions << Array(_compile_filter(options[:if])) end unless options[:unless].empty? conditions << Array(_compile_filter(options[:unless])).map {|f| "!#{f}"} end @compiled_options = conditions.flatten.join(" && ") 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(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", :scope => [ :kind ] }.merge(config) end def compile method = [] method << "value = nil" method << "halted = false" callbacks = "value = !halted && (!block_given? || yield)" reverse_each do |callback| callbacks = callback.apply(callbacks) end method << callbacks method << "value" method.join("\n") end end module ClassMethods # This method defines callback chain method for the given kind # if it was not yet defined. # This generated method plays caching role. def __define_callbacks(kind, object) #:nodoc: chain = object.send("_#{kind}_callbacks") name = "_run_callbacks_#{chain.object_id.abs}" unless object.respond_to?(name, true) class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1 def #{name}() #{chain.compile} end protected :#{name} RUBY_EVAL end name end # This is used internally to append, prepend and skip callbacks to the # CallbackChain. def __update_callbacks(name, filters = [], block = nil) #:nodoc: type = filters.first.in?([:before, :after, :around]) ? 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 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. 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) 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) end self.send("_#{symbol}_callbacks=", callbacks.dup.clear) 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. # # * :skip_after_callbacks_if_terminated - Determines if after callbacks should be terminated # by the :terminator option. By default after callbacks executed no matter # if callback chain was terminated or not. # Option makes sence only when :terminator option is specified. # # * :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)) end end end end end