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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 <tt>before_foo</tt> 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 <tt>:scope</tt>
# 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
#
# * <tt>:if</tt> - A symbol naming an instance method or a proc; the
# callback will be called only when it returns a +true+ value.
# * <tt>:unless</tt> - A symbol naming an instance method or a proc; the
# callback will be called only when it returns a +false+ value.
# * <tt>:prepend</tt> - 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+, <tt>:if</tt> or
# <tt>:unless</tt> 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(name)
callbacks = get_callbacks name
ActiveSupport::DescendantsTracker.descendants(self).each do |target|
chain = target.get_callbacks(name).dup
callbacks.each { |c| chain.delete(c) }
target.set_callbacks name, chain
end
self.set_callbacks name, callbacks.dup.clear
end
# Define sets of events in the object lifecycle that support callbacks.
#
# define_callbacks :validate
# define_callbacks :initialize, :save, :destroy
#
# ===== Options
#
# * <tt>:terminator</tt> - Determines when a before filter will halt the
# callback chain, preventing following callbacks from being called and
# the event from being triggered. This should be a lambda to be executed.
# The current object and the return result of the callback will be called
# with the lambda.
#
# define_callbacks :validate, terminator: ->(target,result) { 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.
#
# * <tt>:skip_after_callbacks_if_terminated</tt> - Determines if after
# callbacks should be terminated by the <tt>:terminator</tt> option. By
# default after callbacks executed no matter if callback chain was
# terminated or not. Option makes sense only when <tt>:terminator</tt>
# option is specified.
#
# * <tt>:scope</tt> - 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
# <tt>Audit#before</tt> will be called. On the other hand
#
# define_callbacks :save, scope: [:kind, :name]
#
# would trigger <tt>Audit#before_save</tt> instead. That's constructed
# by calling <tt>#{kind}_#{name}</tt> 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 <tt>Audit#save</tt>.
def define_callbacks(*names)
config = names.last.is_a?(Hash) ? names.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
names.each do |name|
class_attribute "_#{name}_callbacks"
set_callbacks name, CallbackChain.new(name, 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
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