544 lines
18 KiB
Ruby
544 lines
18 KiB
Ruby
require 'active_support/concern'
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require 'active_support/descendants_tracker'
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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 'active_support/core_ext/object/inclusion'
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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 relevant
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# to the other functionality it supplies, so that subclasses can install callbacks
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# that enhance or modify the base functionality without needing to override
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# 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 lifecycle
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# that will support callbacks (via +ClassMethods.define_callbacks+), set the instance
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# methods, procs, or callback objects to be called (via +ClassMethods.set_callback+),
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# and run the installed callbacks at the appropriate times (via +run_callbacks+).
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#
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# Three kinds of callbacks are supported: before callbacks, run before a certain event;
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# after callbacks, run after the event; and around callbacks, blocks that surround the
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# event, triggering it when they yield. Callback code can be contained in instance
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# methods, procs or lambdas, or callback objects that respond to certain predetermined
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# methods. See +ClassMethods.set_callback+ for details.
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#
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# ==== Example
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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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#
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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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# 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 order.
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#
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# If the callback chain was halted, returns +false+. Otherwise returns the result
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# 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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#
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def run_callbacks(kind, key = nil, &block)
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#TODO: deprecate key argument
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self.class.__run_callbacks(kind, self, &block)
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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 overriden 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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class Callback #:nodoc:#
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@@_callback_sequence = 0
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attr_accessor :chain, :filter, :kind, :options, :klass, :raw_filter
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def initialize(chain, filter, kind, options, klass)
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@chain, @kind, @klass = chain, kind, klass
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deprecate_per_key_option(options)
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normalize_options!(options)
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@raw_filter, @options = filter, options
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@filter = _compile_filter(filter)
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recompile_options!
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end
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def deprecate_per_key_option(options)
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if options[:per_key]
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raise NotImplementedError, ":per_key option is no longer supported. Use generic :if and :unless options instead."
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end
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end
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def clone(chain, klass)
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obj = super()
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obj.chain = chain
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obj.klass = klass
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obj.options = @options.dup
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obj.options[:if] = @options[:if].dup
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obj.options[:unless] = @options[:unless].dup
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obj
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end
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def normalize_options!(options)
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options[:if] = Array(options[:if])
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options[:unless] = Array(options[:unless])
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end
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def name
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chain.name
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end
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def next_id
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@@_callback_sequence += 1
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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 _update_filter(filter_options, new_options)
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filter_options[:if].concat(Array(new_options[:unless])) if new_options.key?(:unless)
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filter_options[:unless].concat(Array(new_options[:if])) if new_options.key?(:if)
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end
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def recompile!(_options)
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deprecate_per_key_option(_options)
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_update_filter(self.options, _options)
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recompile_options!
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end
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# Wraps code with filter
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def apply(code)
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case @kind
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when :before
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<<-RUBY_EVAL
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if !halted && #{@compiled_options}
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# This double assignment is to prevent warnings in 1.9.3 as
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# the `result` variable is not always used except if the
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# terminator code refers to it.
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result = result = #{@filter}
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halted = (#{chain.config[:terminator]})
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if halted
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halted_callback_hook(#{@raw_filter.inspect.inspect})
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end
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end
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#{code}
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RUBY_EVAL
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when :after
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<<-RUBY_EVAL
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#{code}
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if #{!chain.config[:skip_after_callbacks_if_terminated] || "!halted"} && #{@compiled_options}
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#{@filter}
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end
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RUBY_EVAL
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when :around
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name = define_conditional_callback
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<<-RUBY_EVAL
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#{name}(halted) do
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#{code}
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value
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end
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RUBY_EVAL
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end
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end
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private
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# Compile around filters with conditions into proxy methods
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# that contain the conditions.
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#
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# For `around_save :filter_name, :if => :condition':
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#
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# def _conditional_callback_save_17
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# if condition
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# filter_name do
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# yield self
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# end
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# else
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# yield self
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# end
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# end
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#
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def define_conditional_callback
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name = "_conditional_callback_#{@kind}_#{next_id}"
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@klass.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
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def #{name}(halted)
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if #{@compiled_options} && !halted
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#{@filter} do
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yield self
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end
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else
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yield self
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end
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end
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RUBY_EVAL
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name
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end
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# Options support the same options as filters themselves (and support
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# symbols, string, procs, and objects), so compile a conditional
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# expression based on the options
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def recompile_options!
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conditions = ["true"]
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unless options[:if].empty?
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conditions << Array(_compile_filter(options[:if]))
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end
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unless options[:unless].empty?
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conditions << Array(_compile_filter(options[:unless])).map {|f| "!#{f}"}
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end
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@compiled_options = conditions.flatten.join(" && ")
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end
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# Filters support:
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#
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# Arrays:: Used in conditions. This is used to specify
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# multiple conditions. Used internally to
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# merge conditions from skip_* filters
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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 before_foo 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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# Arrays:: Merged together into a single filter
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# Symbols:: Already methods
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# Strings:: class_eval'ed into methods
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# Procs:: define_method'ed 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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#
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def _compile_filter(filter)
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method_name = "_callback_#{@kind}_#{next_id}"
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case filter
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when Array
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filter.map {|f| _compile_filter(f)}
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when Symbol
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filter
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when String
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"(#{filter})"
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when Proc
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@klass.send(:define_method, method_name, &filter)
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return method_name if filter.arity <= 0
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method_name << (filter.arity == 1 ? "(self)" : " self, Proc.new ")
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else
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@klass.send(:define_method, "#{method_name}_object") { filter }
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_normalize_legacy_filter(kind, filter)
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scopes = Array(chain.config[:scope])
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method_to_call = scopes.map{ |s| s.is_a?(Symbol) ? send(s) : s }.join("_")
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@klass.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
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def #{method_name}(&blk)
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#{method_name}_object.send(:#{method_to_call}, self, &blk)
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end
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RUBY_EVAL
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method_name
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end
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end
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def _normalize_legacy_filter(kind, filter)
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if !filter.respond_to?(kind) && filter.respond_to?(:filter)
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filter.singleton_class.class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
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def #{kind}(context, &block) filter(context, &block) end
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RUBY_EVAL
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elsif filter.respond_to?(:before) && filter.respond_to?(:after) && kind == :around
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def filter.around(context)
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should_continue = before(context)
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yield if should_continue
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after(context)
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end
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end
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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 < Array #:nodoc:#
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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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:terminator => "false",
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:scope => [ :kind ]
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}.merge(config)
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end
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def compile
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method = []
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method << "value = nil"
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method << "halted = false"
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callbacks = "value = yield if block_given? && !halted"
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reverse_each do |callback|
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callbacks = callback.apply(callbacks)
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end
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method << callbacks
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method << "halted ? false : (block_given? ? value : true)"
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method.flatten.compact.join("\n")
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end
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end
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module ClassMethods
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# This method runs callback chain for the given kind.
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# If this called first time it creates a new callback method for the kind.
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# This generated method plays caching role.
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#
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def __run_callbacks(kind, object, &blk) #:nodoc:
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name = __callback_runner_name(kind)
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unless object.respond_to?(name, true)
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str = object.send("_#{kind}_callbacks").compile
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class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
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def #{name}() #{str} end
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protected :#{name}
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RUBY_EVAL
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end
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object.send(name, &blk)
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end
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def __reset_runner(symbol)
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name = __callback_runner_name(symbol)
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undef_method(name) if method_defined?(name)
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end
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def __callback_runner_name(kind)
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"_run__#{self.name.hash.abs}__#{kind}__callbacks"
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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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#
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def __update_callbacks(name, filters = [], block = nil) #:nodoc:
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type = filters.first.in?([:before, :after, :around]) ? filters.shift : :before
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options = filters.last.is_a?(Hash) ? filters.pop : {}
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filters.unshift(block) if block
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([self] + ActiveSupport::DescendantsTracker.descendants(self)).reverse.each do |target|
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chain = target.send("_#{name}_callbacks")
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yield target, chain.dup, type, filters, options
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target.__reset_runner(name)
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end
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end
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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, lambda { |r| stuff; result = yield; 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 specified as a symbol naming an instance method; as a proc,
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# lambda, or block; as a string to be instance evaluated; or as an object that
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# responds to a certain method determined by the <tt>:scope</tt> argument to
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# +define_callback+.
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#
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# If a proc, lambda, or block is given, its body is evaluated in the context
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# of the current object. It can also optionally accept the current object as
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# an argument.
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#
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# Before and around callbacks are called in the order that they are set; after
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# callbacks are called in the reverse order.
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#
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# Around callbacks can access the return value from the event, if it
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# wasn't halted, from the +yield+ call.
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#
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# ===== Options
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#
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# * <tt>:if</tt> - A symbol naming an instance method or a proc; the callback
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# will be called only when it returns a true value.
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# * <tt>:unless</tt> - A symbol naming an instance method or a proc; the callback
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# will be called only when it returns a false value.
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# * <tt>:prepend</tt> - If true, the callback will be prepended to the existing
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# chain rather than appended.
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#
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def set_callback(name, *filter_list, &block)
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mapped = nil
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__update_callbacks(name, filter_list, block) do |target, chain, type, filters, options|
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mapped ||= filters.map do |filter|
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Callback.new(chain, filter, type, options.dup, self)
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end
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filters.each do |filter|
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chain.delete_if {|c| c.matches?(type, filter) }
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end
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options[:prepend] ? chain.unshift(*(mapped.reverse)) : chain.push(*mapped)
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target.send("_#{name}_callbacks=", chain)
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end
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end
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# Skip a previously set callback. Like +set_callback+, <tt>:if</tt> or <tt>:unless</tt>
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# options may be passed in order to control when the callback is skipped.
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#
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# class Writer < Person
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# skip_callback :validate, :before, :check_membership, :if => lambda { self.age > 18 }
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# end
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#
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def skip_callback(name, *filter_list, &block)
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__update_callbacks(name, filter_list, block) do |target, chain, type, filters, options|
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filters.each do |filter|
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filter = chain.find {|c| c.matches?(type, filter) }
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if filter && options.any?
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new_filter = filter.clone(chain, self)
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chain.insert(chain.index(filter), new_filter)
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new_filter.recompile!(options)
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end
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chain.delete(filter)
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end
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target.send("_#{name}_callbacks=", chain)
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end
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end
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# Remove all set callbacks for the given event.
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#
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def reset_callbacks(symbol)
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callbacks = send("_#{symbol}_callbacks")
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ActiveSupport::DescendantsTracker.descendants(self).each do |target|
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chain = target.send("_#{symbol}_callbacks").dup
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callbacks.each { |c| chain.delete(c) }
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target.send("_#{symbol}_callbacks=", chain)
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target.__reset_runner(symbol)
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end
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self.send("_#{symbol}_callbacks=", callbacks.dup.clear)
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__reset_runner(symbol)
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end
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# Define sets of events in the object lifecycle that support callbacks.
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#
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# define_callbacks :validate
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# define_callbacks :initialize, :save, :destroy
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#
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# ===== Options
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#
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# * <tt>:terminator</tt> - Determines when a before filter will halt the callback
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# chain, preventing following callbacks from being called and the event from being
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# triggered. This is a string to be eval'ed. The result of the callback is available
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# in the <tt>result</tt> variable.
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#
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# define_callbacks :validate, :terminator => "result == false"
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#
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# In this example, if any before validate callbacks returns +false+,
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# other callbacks are not executed. Defaults to "false", meaning no value
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# halts the chain.
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#
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# * <tt>:skip_after_callbacks_if_terminated</tt> - Determines if after callbacks should be terminated
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# by the <tt>:terminator</tt> option. By default after callbacks executed no matter
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# if callback chain was terminated or not.
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# Option makes sence only when <tt>:terminator</tt> option is specified.
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#
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# * <tt>:scope</tt> - Indicates which methods should be executed when an object
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# is used as a callback.
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#
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# class Audit
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# def before(caller)
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# puts 'Audit: before is called'
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# end
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#
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# def before_save(caller)
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# puts 'Audit: before_save is called'
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# end
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# end
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#
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# class Account
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# include ActiveSupport::Callbacks
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#
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# define_callbacks :save
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# set_callback :save, :before, Audit.new
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#
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# def save
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# run_callbacks :save do
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# puts 'save in main'
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# end
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# end
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# end
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#
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# In the above case whenever you save an account the method <tt>Audit#before</tt> will
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# be called. On the other hand
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#
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# define_callbacks :save, :scope => [:kind, :name]
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#
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# would trigger <tt>Audit#before_save</tt> instead. That's constructed by calling
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# <tt>#{kind}_#{name}</tt> on the given instance. In this case "kind" is "before" and
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# "name" is "save". In this context +:kind+ and +:name+ have special meanings: +:kind+
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# refers to the kind of callback (before/after/around) and +:name+ refers to the
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# method on which callbacks are being defined.
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#
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# A declaration like
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#
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# define_callbacks :save, :scope => [:name]
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|
#
|
|
# would call <tt>Audit#save</tt>.
|
|
#
|
|
def define_callbacks(*callbacks)
|
|
config = callbacks.last.is_a?(Hash) ? callbacks.pop : {}
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|
callbacks.each do |callback|
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|
class_attribute "_#{callback}_callbacks"
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|
send("_#{callback}_callbacks=", CallbackChain.new(callback, config))
|
|
end
|
|
end
|
|
end
|
|
end
|
|
end
|