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 'thread' 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 CALLBACK_FILTER_TYPES = [:before, :after, :around] # 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) cbs = send("_#{kind}_callbacks") if cbs.empty? yield if block_given? else runner = cbs.compile e = Filters::Environment.new(self, false, nil, block) runner.call(e).value end end private # A hook invoked everytime a before callback is halted. # This can be overridden in AS::Callback implementors in order # to provide better debugging/logging. def halted_callback_hook(filter) end module Conditionals # :nodoc: class Value def initialize(&block) @block = block end def call(target, value); @block.call(value); end end end module Filters Environment = Struct.new(:target, :halted, :value, :run_block) class End def call(env) block = env.run_block env.value = !env.halted && (!block || block.call) env end end ENDING = End.new class Before def self.build(next_callback, user_callback, user_conditions, chain_config, filter) halted_lambda = chain_config[:terminator] if chain_config.key?(:terminator) && user_conditions.any? halting_and_conditional(next_callback, user_callback, user_conditions, halted_lambda, filter) elsif chain_config.key? :terminator halting(next_callback, user_callback, halted_lambda, filter) elsif user_conditions.any? conditional(next_callback, user_callback, user_conditions) else simple next_callback, user_callback end end private def self.halting_and_conditional(next_callback, user_callback, user_conditions, halted_lambda, filter) lambda { |env| target = env.target value = env.value halted = env.halted if !halted && user_conditions.all? { |c| c.call(target, value) } result = user_callback.call target, value env.halted = halted_lambda.call(target, result) if env.halted target.send :halted_callback_hook, filter end end next_callback.call env } end def self.halting(next_callback, user_callback, halted_lambda, filter) lambda { |env| target = env.target value = env.value halted = env.halted unless halted result = user_callback.call target, value env.halted = halted_lambda.call(target, result) if env.halted target.send :halted_callback_hook, filter end end next_callback.call env } end def self.conditional(next_callback, user_callback, user_conditions) lambda { |env| target = env.target value = env.value if user_conditions.all? { |c| c.call(target, value) } user_callback.call target, value end next_callback.call env } end def self.simple(next_callback, user_callback) lambda { |env| user_callback.call env.target, env.value next_callback.call env } end end class After def self.build(next_callback, user_callback, user_conditions, chain_config) if chain_config[:skip_after_callbacks_if_terminated] if chain_config.key?(:terminator) && user_conditions.any? halting_and_conditional(next_callback, user_callback, user_conditions) elsif chain_config.key?(:terminator) halting(next_callback, user_callback) elsif user_conditions.any? conditional next_callback, user_callback, user_conditions else simple next_callback, user_callback end else if user_conditions.any? conditional next_callback, user_callback, user_conditions else simple next_callback, user_callback end end end private def self.halting_and_conditional(next_callback, user_callback, user_conditions) lambda { |env| env = next_callback.call env target = env.target value = env.value halted = env.halted if !halted && user_conditions.all? { |c| c.call(target, value) } user_callback.call target, value end env } end def self.halting(next_callback, user_callback) lambda { |env| env = next_callback.call env unless env.halted user_callback.call env.target, env.value end env } end def self.conditional(next_callback, user_callback, user_conditions) lambda { |env| env = next_callback.call env target = env.target value = env.value if user_conditions.all? { |c| c.call(target, value) } user_callback.call target, value end env } end def self.simple(next_callback, user_callback) lambda { |env| env = next_callback.call env user_callback.call env.target, env.value env } end end class Around def self.build(next_callback, user_callback, user_conditions, chain_config) if chain_config.key?(:terminator) && user_conditions.any? halting_and_conditional(next_callback, user_callback, user_conditions) elsif chain_config.key? :terminator halting(next_callback, user_callback) elsif user_conditions.any? conditional(next_callback, user_callback, user_conditions) else simple(next_callback, user_callback) end end private def self.halting_and_conditional(next_callback, user_callback, user_conditions) lambda { |env| target = env.target value = env.value halted = env.halted if !halted && user_conditions.all? { |c| c.call(target, value) } user_callback.call(target, value) { env = next_callback.call env env.value } env else next_callback.call env end } end def self.halting(next_callback, user_callback) lambda { |env| target = env.target value = env.value unless env.halted user_callback.call(target, value) { env = next_callback.call env env.value } env else next_callback.call env end } end def self.conditional(next_callback, user_callback, user_conditions) lambda { |env| target = env.target value = env.value if user_conditions.all? { |c| c.call(target, value) } user_callback.call(target, value) { env = next_callback.call env env.value } env else next_callback.call env end } end def self.simple(next_callback, user_callback) lambda { |env| user_callback.call(env.target, env.value) { env = next_callback.call env env.value } env } end end end class Callback #:nodoc:# def self.build(chain, filter, kind, options) new chain.name, filter, kind, options, chain.config end attr_accessor :kind, :name attr_reader :chain_config def initialize(name, filter, kind, options, chain_config) @chain_config = chain_config @name = name @kind = kind @filter = filter @key = compute_identifier filter @if = Array(options[:if]) @unless = Array(options[:unless]) end def filter; @key; end def raw_filter; @filter; end def merge(chain, new_options) options = { :if => @if.dup, :unless => @unless.dup } options[:if].concat Array(new_options.fetch(:unless, [])) options[:unless].concat Array(new_options.fetch(:if, [])) self.class.build chain, @filter, @kind, options end def matches?(_kind, _filter) @kind == _kind && filter == _filter end def duplicates?(other) case @filter when Symbol, String matches?(other.kind, other.filter) else false end end # Wraps code with filter def apply(next_callback) user_conditions = conditions_lambdas user_callback = make_lambda @filter case kind when :before Filters::Before.build(next_callback, user_callback, user_conditions, chain_config, @filter) when :after Filters::After.build(next_callback, user_callback, user_conditions, chain_config) when :around Filters::Around.build(next_callback, user_callback, user_conditions, chain_config) end end private def invert_lambda(l) lambda { |*args, &blk| !l.call(*args, &blk) } end # Filters support: # # 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: # # Symbols:: Already methods. # Strings:: class_eval'd into methods. # Procs:: using define_method compiled into methods. # Objects:: # a method is created that calls the before_foo method # on the object. def make_lambda(filter) case filter when Symbol lambda { |target, _, &blk| target.send filter, &blk } when String l = eval "lambda { |value| #{filter} }" lambda { |target, value| target.instance_exec(value, &l) } when Conditionals::Value then filter when ::Proc if filter.arity > 1 return lambda { |target, _, &block| raise ArgumentError unless block target.instance_exec(target, block, &filter) } end if filter.arity <= 0 lambda { |target, _| target.instance_exec(&filter) } else lambda { |target, _| target.instance_exec(target, &filter) } end else scopes = Array(chain_config[:scope]) method_to_call = scopes.map{ |s| public_send(s) }.join("_") lambda { |target, _, &blk| filter.public_send method_to_call, target, &blk } end end def compute_identifier(filter) case filter when String, ::Proc filter.object_id else filter end end def conditions_lambdas @if.map { |c| make_lambda c } + @unless.map { |c| invert_lambda make_lambda c } end end # An Array with a compile method. class CallbackChain #:nodoc:# include Enumerable attr_reader :name, :config def initialize(name, config) @name = name @config = { :scope => [ :kind ] }.merge!(config) @chain = [] @callbacks = nil @mutex = Mutex.new end def each(&block); @chain.each(&block); end def index(o); @chain.index(o); end def empty?; @chain.empty?; end def insert(index, o) @callbacks = nil @chain.insert(index, o) end def delete(o) @callbacks = nil @chain.delete(o) end def clear @callbacks = nil @chain.clear self end def initialize_copy(other) @callbacks = nil @chain = other.chain.dup @mutex = Mutex.new end def compile @callbacks || @mutex.synchronize do @callbacks ||= @chain.reverse.inject(Filters::ENDING) do |chain, callback| callback.apply chain end end end def append(*callbacks) callbacks.each { |c| append_one(c) } end def prepend(*callbacks) callbacks.each { |c| prepend_one(c) } end protected def chain; @chain; end private def append_one(callback) @callbacks = nil remove_duplicates(callback) @chain.push(callback) end def prepend_one(callback) @callbacks = nil remove_duplicates(callback) @chain.unshift(callback) end def remove_duplicates(callback) @callbacks = nil @chain.delete_if { |c| callback.duplicates?(c) } end end module ClassMethods def normalize_callback_params(filters, block) # :nodoc: type = CALLBACK_FILTER_TYPES.include?(filters.first) ? filters.shift : :before options = filters.last.is_a?(Hash) ? filters.pop : {} filters.unshift(block) if block [type, filters, options.dup] end # This is used internally to append, prepend and skip callbacks to the # CallbackChain. def __update_callbacks(name) #:nodoc: ([self] + ActiveSupport::DescendantsTracker.descendants(self)).reverse.each do |target| chain = target.get_callbacks name yield target, chain.dup 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, ->(r, &block) { stuff; result = block.call; 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) type, filters, options = normalize_callback_params(filter_list, block) self_chain = get_callbacks name mapped = filters.map do |filter| Callback.build(self_chain, filter, type, options) end __update_callbacks(name) do |target, chain| options[:prepend] ? chain.prepend(*mapped) : chain.append(*mapped) target.set_callbacks name, 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: -> { self.age > 18 } # end def skip_callback(name, *filter_list, &block) type, filters, options = normalize_callback_params(filter_list, block) __update_callbacks(name) do |target, chain| filters.each do |filter| filter = chain.find {|c| c.matches?(type, filter) } if filter && options.any? new_filter = filter.merge(chain, options) chain.insert(chain.index(filter), new_filter) end chain.delete(filter) end target.set_callbacks name, chain end end # Remove all set callbacks for the given event. def reset_callbacks(symbol) callbacks = get_callbacks symbol ActiveSupport::DescendantsTracker.descendants(self).each do |target| chain = target.get_callbacks(symbol).dup callbacks.each { |c| chain.delete(c) } target.set_callbacks symbol, chain end self.set_callbacks symbol, 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'd. 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 sense 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 : {} if config.key?(:terminator) && String === config[:terminator] ActiveSupport::Deprecation.warn "String based terminators are deprecated, please use a lambda" value = config[:terminator] l = class_eval "lambda { |result| #{value} }", __FILE__, __LINE__ config[:terminator] = lambda { |target, result| target.instance_exec(result, &l) } end callbacks.each do |callback| class_attribute "_#{callback}_callbacks" set_callbacks callback, CallbackChain.new(callback, config) end end protected def get_callbacks(name) send "_#{name}_callbacks" end def set_callbacks(name, callbacks) send "_#{name}_callbacks=", callbacks end end end end