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, name)
@kind, @klass = kind, klass
@name = name
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, _name, _filter)
@kind == _kind &&
@name == _name &&
@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 = <<-RUBY_EVAL
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)
"#{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 Proc
@klass.send(:define_method, method_name, &filter)
method_name << (filter.arity == 1 ? "(self)" : "")
when String
@klass.class_eval <<-RUBY_EVAL
def #{method_name}
#{filter}
end
RUBY_EVAL
method_name
else
kind, name = @kind, @name
@klass.send(:define_method, method_name) do
filter.send("#{kind}_#{name}", self)
end
method_name
end
end
end
# This method_missing is supplied to catch callbacks with keys and create
# the appropriate callback for future use.
def method_missing(meth, *args, &blk)
if meth.to_s =~ /_run__([\w:]+)__(\w+)__(\w+)__callbacks/
return self.class._create_and_run_keyed_callback($1, $2.to_sym, $3.to_sym, self, &blk)
end
super
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?"
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, str, options)
str = <<-RUBY_EVAL
def _run_#{symbol}_callbacks(key = nil)
if key
key = key.hash.to_s.gsub(/-/, '_')
name = "_run__\#{self.class.name.split("::").last}__#{symbol}__\#{key}__callbacks"
if respond_to?(name)
send(name) { yield if block_given? }
else
self.class._create_and_run_keyed_callback(
self.class.name.split("::").last,
:#{symbol}, key, self) { yield if block_given? }
end
else
#{str}
end
end
RUBY_EVAL
undef_method "_run_#{symbol}_callbacks" if method_defined?("_run_#{symbol}_callbacks")
class_eval str, __FILE__, __LINE__
before_name, around_name, after_name =
options.values_at(:before, :after, :around)
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_and_run_keyed_callback(klass, kind, key, obj, &blk)
@_keyed_callbacks ||= {}
@_keyed_callbacks[[kind, key]] ||= begin
str = self.send("_#{kind}_callbacks").compile(key, :object => obj, :terminator => self.send("_#{kind}_terminator"))
self.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
def _run__#{klass.split("::").last}__#{kind}__#{key}__callbacks
#{str}
end
RUBY_EVAL
true
end
obj.send("_run__#{klass.split("::").last}__#{kind}__#{key}__callbacks", &blk)
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 define_callbacks(*symbols)
terminator = symbols.pop if symbols.last.is_a?(String)
symbols.each do |symbol|
self.extlib_inheritable_accessor("_#{symbol}_terminator")
self.send("_#{symbol}_terminator=", terminator)
self.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
extlib_inheritable_accessor :_#{symbol}_callbacks
self._#{symbol}_callbacks = CallbackChain.new(:#{symbol})
def self.#{symbol}_callback(*filters, &blk)
type = [:before, :after, :around].include?(filters.first) ? filters.shift : :before
options = filters.last.is_a?(Hash) ? filters.pop : {}
filters.unshift(blk) if block_given?
filters.map! do |filter|
# overrides parent class
self._#{symbol}_callbacks.delete_if {|c| c.matches?(type, :#{symbol}, filter)}
Callback.new(filter, type, options.dup, self, :#{symbol})
end
self._#{symbol}_callbacks.push(*filters)
_define_runner(:#{symbol},
self._#{symbol}_callbacks.compile(nil, :terminator => _#{symbol}_terminator),
options)
end
def self.skip_#{symbol}_callback(*filters, &blk)
type = [:before, :after, :around].include?(filters.first) ? filters.shift : :before
options = filters.last.is_a?(Hash) ? filters.pop : {}
filters.unshift(blk) if block_given?
filters.each do |filter|
self._#{symbol}_callbacks = self._#{symbol}_callbacks.clone(self)
filter = self._#{symbol}_callbacks.find {|c| c.matches?(type, :#{symbol}, filter) }
per_key = options[:per_key] || {}
if filter
filter.recompile!(options, per_key)
else
self._#{symbol}_callbacks.delete(filter)
end
_define_runner(:#{symbol},
self._#{symbol}_callbacks.compile(nil, :terminator => _#{symbol}_terminator),
options)
end
end
def self.reset_#{symbol}_callbacks
self._#{symbol}_callbacks = CallbackChain.new(:#{symbol})
_define_runner(:#{symbol}, self._#{symbol}_callbacks.compile, {})
end
self.#{symbol}_callback(:before)
RUBY_EVAL
end
end
end
end
end
