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745 lines
23 KiB
Ruby
745 lines
23 KiB
Ruby
require 'active_support/concern'
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require 'active_support/descendants_tracker'
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require 'active_support/core_ext/array/extract_options'
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require 'active_support/core_ext/class/attribute'
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require 'active_support/core_ext/kernel/reporting'
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require 'active_support/core_ext/kernel/singleton_class'
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require 'thread'
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module ActiveSupport
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# Callbacks are code hooks that are run at key points in an object's lifecycle.
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# The typical use case is to have a base class define a set of callbacks
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# relevant to the other functionality it supplies, so that subclasses can
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# install callbacks that enhance or modify the base functionality without
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# needing to override or redefine methods of the base class.
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#
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# Mixing in this module allows you to define the events in the object's
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# lifecycle that will support callbacks (via +ClassMethods.define_callbacks+),
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# set the instance methods, procs, or callback objects to be called (via
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# +ClassMethods.set_callback+), and run the installed callbacks at the
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# appropriate times (via +run_callbacks+).
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#
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# Three kinds of callbacks are supported: before callbacks, run before a
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# certain event; after callbacks, run after the event; and around callbacks,
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# blocks that surround the event, triggering it when they yield. Callback code
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# can be contained in instance methods, procs or lambdas, or callback objects
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# that respond to certain predetermined methods. See +ClassMethods.set_callback+
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# for details.
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#
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# class Record
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# include ActiveSupport::Callbacks
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# define_callbacks :save
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#
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# def save
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# run_callbacks :save do
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# puts "- save"
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# end
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# end
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# end
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#
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# class PersonRecord < Record
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# set_callback :save, :before, :saving_message
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# def saving_message
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# puts "saving..."
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# end
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#
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# set_callback :save, :after do |object|
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# puts "saved"
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# end
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# end
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#
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# person = PersonRecord.new
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# person.save
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#
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# Output:
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# saving...
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# - save
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# saved
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module Callbacks
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extend Concern
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included do
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extend ActiveSupport::DescendantsTracker
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end
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CALLBACK_FILTER_TYPES = [:before, :after, :around]
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# Runs the callbacks for the given event.
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#
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# Calls the before and around callbacks in the order they were set, yields
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# the block (if given one), and then runs the after callbacks in reverse
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# order.
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#
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# If the callback chain was halted, returns +false+. Otherwise returns the
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# result of the block, or +true+ if no block is given.
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#
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# run_callbacks :save do
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# save
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# end
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def run_callbacks(kind, &block)
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cbs = send("_#{kind}_callbacks")
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if cbs.empty?
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yield if block_given?
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else
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runner = cbs.compile
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e = Filters::Environment.new(self, false, nil, block)
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runner.call(e).value
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end
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end
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private
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# A hook invoked everytime a before callback is halted.
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# This can be overridden in AS::Callback implementors in order
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# to provide better debugging/logging.
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def halted_callback_hook(filter)
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end
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module Conditionals # :nodoc:
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class Value
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def initialize(&block)
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@block = block
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end
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def call(target, value); @block.call(value); end
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end
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end
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module Filters
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Environment = Struct.new(:target, :halted, :value, :run_block)
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class End
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def call(env)
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block = env.run_block
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env.value = !env.halted && (!block || block.call)
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env
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end
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end
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ENDING = End.new
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class Before
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def self.build(next_callback, user_callback, user_conditions, chain_config, filter)
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halted_lambda = chain_config[:terminator]
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if chain_config.key?(:terminator) && user_conditions.any?
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halting_and_conditional(next_callback, user_callback, user_conditions, halted_lambda, filter)
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elsif chain_config.key? :terminator
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halting(next_callback, user_callback, halted_lambda, filter)
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elsif user_conditions.any?
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conditional(next_callback, user_callback, user_conditions)
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else
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simple next_callback, user_callback
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end
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end
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private
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def self.halting_and_conditional(next_callback, user_callback, user_conditions, halted_lambda, filter)
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lambda { |env|
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target = env.target
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value = env.value
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halted = env.halted
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if !halted && user_conditions.all? { |c| c.call(target, value) }
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result = user_callback.call target, value
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env.halted = halted_lambda.call(target, result)
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if env.halted
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target.send :halted_callback_hook, filter
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end
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end
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next_callback.call env
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}
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end
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def self.halting(next_callback, user_callback, halted_lambda, filter)
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lambda { |env|
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target = env.target
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value = env.value
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halted = env.halted
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unless halted
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result = user_callback.call target, value
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env.halted = halted_lambda.call(target, result)
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if env.halted
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target.send :halted_callback_hook, filter
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end
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end
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next_callback.call env
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}
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end
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def self.conditional(next_callback, user_callback, user_conditions)
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lambda { |env|
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target = env.target
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value = env.value
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if user_conditions.all? { |c| c.call(target, value) }
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user_callback.call target, value
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end
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next_callback.call env
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}
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end
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def self.simple(next_callback, user_callback)
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lambda { |env|
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user_callback.call env.target, env.value
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next_callback.call env
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}
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end
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end
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class After
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def self.build(next_callback, user_callback, user_conditions, chain_config)
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if chain_config[:skip_after_callbacks_if_terminated]
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if chain_config.key?(:terminator) && user_conditions.any?
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halting_and_conditional(next_callback, user_callback, user_conditions)
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elsif chain_config.key?(:terminator)
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halting(next_callback, user_callback)
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elsif user_conditions.any?
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conditional next_callback, user_callback, user_conditions
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else
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simple next_callback, user_callback
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end
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else
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if user_conditions.any?
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conditional next_callback, user_callback, user_conditions
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else
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simple next_callback, user_callback
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end
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end
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end
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private
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def self.halting_and_conditional(next_callback, user_callback, user_conditions)
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lambda { |env|
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env = next_callback.call env
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target = env.target
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value = env.value
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halted = env.halted
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if !halted && user_conditions.all? { |c| c.call(target, value) }
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user_callback.call target, value
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end
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env
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}
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end
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def self.halting(next_callback, user_callback)
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lambda { |env|
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env = next_callback.call env
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unless env.halted
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user_callback.call env.target, env.value
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end
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env
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}
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end
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def self.conditional(next_callback, user_callback, user_conditions)
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lambda { |env|
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env = next_callback.call env
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target = env.target
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value = env.value
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if user_conditions.all? { |c| c.call(target, value) }
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user_callback.call target, value
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end
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env
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}
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end
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def self.simple(next_callback, user_callback)
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lambda { |env|
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env = next_callback.call env
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user_callback.call env.target, env.value
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env
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}
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end
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end
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class Around
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def self.build(next_callback, user_callback, user_conditions, chain_config)
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if chain_config.key?(:terminator) && user_conditions.any?
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halting_and_conditional(next_callback, user_callback, user_conditions)
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elsif chain_config.key? :terminator
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halting(next_callback, user_callback)
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elsif user_conditions.any?
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conditional(next_callback, user_callback, user_conditions)
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else
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simple(next_callback, user_callback)
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end
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end
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private
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def self.halting_and_conditional(next_callback, user_callback, user_conditions)
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lambda { |env|
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target = env.target
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value = env.value
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halted = env.halted
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if !halted && user_conditions.all? { |c| c.call(target, value) }
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user_callback.call(target, value) {
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env = next_callback.call env
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env.value
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}
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env
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else
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next_callback.call env
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end
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}
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end
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def self.halting(next_callback, user_callback)
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lambda { |env|
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target = env.target
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value = env.value
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unless env.halted
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user_callback.call(target, value) {
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env = next_callback.call env
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env.value
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}
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env
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else
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next_callback.call env
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end
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}
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end
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def self.conditional(next_callback, user_callback, user_conditions)
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lambda { |env|
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target = env.target
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value = env.value
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if user_conditions.all? { |c| c.call(target, value) }
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user_callback.call(target, value) {
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env = next_callback.call env
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env.value
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}
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env
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else
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next_callback.call env
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end
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}
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end
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def self.simple(next_callback, user_callback)
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lambda { |env|
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user_callback.call(env.target, env.value) {
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env = next_callback.call env
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env.value
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}
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env
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}
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end
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end
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end
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class Callback #:nodoc:#
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def self.build(chain, filter, kind, options)
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new chain.name, filter, kind, options, chain.config
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end
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attr_accessor :kind, :name
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attr_reader :chain_config
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def initialize(name, filter, kind, options, chain_config)
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@chain_config = chain_config
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@name = name
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@kind = kind
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@filter = filter
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@key = compute_identifier filter
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@if = Array(options[:if])
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@unless = Array(options[:unless])
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end
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def filter; @key; end
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def raw_filter; @filter; end
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def merge(chain, new_options)
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options = {
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:if => @if.dup,
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:unless => @unless.dup
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}
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options[:if].concat Array(new_options.fetch(:unless, []))
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options[:unless].concat Array(new_options.fetch(:if, []))
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self.class.build chain, @filter, @kind, options
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end
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def matches?(_kind, _filter)
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@kind == _kind && filter == _filter
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end
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def duplicates?(other)
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case @filter
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when Symbol, String
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matches?(other.kind, other.filter)
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else
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false
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end
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end
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# Wraps code with filter
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def apply(next_callback)
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user_conditions = conditions_lambdas
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user_callback = make_lambda @filter
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case kind
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when :before
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Filters::Before.build(next_callback, user_callback, user_conditions, chain_config, @filter)
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when :after
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Filters::After.build(next_callback, user_callback, user_conditions, chain_config)
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when :around
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Filters::Around.build(next_callback, user_callback, user_conditions, chain_config)
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end
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end
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private
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def invert_lambda(l)
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lambda { |*args, &blk| !l.call(*args, &blk) }
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end
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# Filters support:
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#
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# Symbols:: A method to call.
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# Strings:: Some content to evaluate.
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# Procs:: A proc to call with the object.
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# Objects:: An object with a <tt>before_foo</tt> method on it to call.
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#
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# All of these objects are compiled into methods and handled
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# the same after this point:
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#
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# Symbols:: Already methods.
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# Strings:: class_eval'd into methods.
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# Procs:: using define_method compiled into methods.
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# Objects::
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# a method is created that calls the before_foo method
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# on the object.
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def make_lambda(filter)
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case filter
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when Symbol
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lambda { |target, _, &blk| target.send filter, &blk }
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when String
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l = eval "lambda { |value| #{filter} }"
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lambda { |target, value| target.instance_exec(value, &l) }
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when Conditionals::Value then filter
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when ::Proc
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if filter.arity > 1
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return lambda { |target, _, &block|
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raise ArgumentError unless block
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target.instance_exec(target, block, &filter)
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}
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end
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if filter.arity <= 0
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lambda { |target, _| target.instance_exec(&filter) }
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else
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lambda { |target, _| target.instance_exec(target, &filter) }
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end
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else
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scopes = Array(chain_config[:scope])
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method_to_call = scopes.map{ |s| public_send(s) }.join("_")
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lambda { |target, _, &blk|
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filter.public_send method_to_call, target, &blk
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}
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end
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end
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def compute_identifier(filter)
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case filter
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when String, ::Proc
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filter.object_id
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else
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filter
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end
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end
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def conditions_lambdas
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@if.map { |c| make_lambda c } +
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@unless.map { |c| invert_lambda make_lambda c }
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end
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end
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# An Array with a compile method.
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class CallbackChain #:nodoc:#
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include Enumerable
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attr_reader :name, :config
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def initialize(name, config)
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@name = name
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@config = {
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:scope => [ :kind ]
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}.merge!(config)
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@chain = []
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@callbacks = nil
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@mutex = Mutex.new
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end
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def each(&block); @chain.each(&block); end
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def index(o); @chain.index(o); end
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def empty?; @chain.empty?; end
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def insert(index, o)
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@callbacks = nil
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@chain.insert(index, o)
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end
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def delete(o)
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@callbacks = nil
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@chain.delete(o)
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end
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def clear
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@callbacks = nil
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@chain.clear
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self
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end
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def initialize_copy(other)
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@callbacks = nil
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@chain = other.chain.dup
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@mutex = Mutex.new
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end
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def compile
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@callbacks || @mutex.synchronize do
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@callbacks ||= @chain.reverse.inject(Filters::ENDING) do |chain, callback|
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callback.apply chain
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end
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end
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end
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def append(*callbacks)
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callbacks.each { |c| append_one(c) }
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end
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def prepend(*callbacks)
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callbacks.each { |c| prepend_one(c) }
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end
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protected
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def chain; @chain; end
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private
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def append_one(callback)
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@callbacks = nil
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remove_duplicates(callback)
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@chain.push(callback)
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end
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def prepend_one(callback)
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@callbacks = nil
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remove_duplicates(callback)
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@chain.unshift(callback)
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end
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def remove_duplicates(callback)
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@callbacks = nil
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@chain.delete_if { |c| callback.duplicates?(c) }
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end
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end
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module ClassMethods
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def normalize_callback_params(filters, block) # :nodoc:
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type = CALLBACK_FILTER_TYPES.include?(filters.first) ? filters.shift : :before
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options = filters.extract_options!
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filters.unshift(block) if block
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[type, filters, options.dup]
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end
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# This is used internally to append, prepend and skip callbacks to the
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# CallbackChain.
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def __update_callbacks(name) #:nodoc:
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([self] + ActiveSupport::DescendantsTracker.descendants(self)).reverse.each do |target|
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chain = target.get_callbacks name
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yield target, chain.dup
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end
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end
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|
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# Install a callback for the given event.
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#
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# set_callback :save, :before, :before_meth
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# set_callback :save, :after, :after_meth, if: :condition
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# set_callback :save, :around, ->(r, &block) { stuff; result = block.call; stuff }
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#
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# The second arguments indicates whether the callback is to be run +:before+,
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# +:after+, or +:around+ the event. If omitted, +:before+ is assumed. This
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# means the first example above can also be written as:
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#
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# set_callback :save, :before_meth
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#
|
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# The callback can be specified as a symbol naming an instance method; as a
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# proc, lambda, or block; as a string to be instance evaluated; or as an
|
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# object that responds to a certain method determined by the <tt>:scope</tt>
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# 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)
|
|
options = names.extract_options!
|
|
if options.key?(:terminator) && String === options[:terminator]
|
|
ActiveSupport::Deprecation.warn "String based terminators are deprecated, please use a lambda"
|
|
value = options[:terminator]
|
|
line = class_eval "lambda { |result| #{value} }", __FILE__, __LINE__
|
|
options[:terminator] = lambda { |target, result| target.instance_exec(result, &line) }
|
|
end
|
|
|
|
names.each do |name|
|
|
class_attribute "_#{name}_callbacks"
|
|
set_callbacks name, CallbackChain.new(name, options)
|
|
end
|
|
end
|
|
|
|
protected
|
|
|
|
def get_callbacks(name)
|
|
send "_#{name}_callbacks"
|
|
end
|
|
|
|
def set_callbacks(name, callbacks)
|
|
send "_#{name}_callbacks=", callbacks
|
|
end
|
|
end
|
|
end
|
|
end
|