Module: ActiveSupport::Callbacks

Defined in:
lib/active_support/callbacks.rb

Overview

Callbacks are hooks into the lifecycle of an object that allow you to trigger logic before or after an alteration of the object state.

Mixing in this module allows you to define callbacks in your class.

Example:

class Storage
include ActiveSupport::Callbacks

define_callbacks :before_save, :after_save
end

class ConfigStorage < Storage
before_save :saving_message
def saving_message
  puts "saving..."
end

after_save do |object|
  puts "saved"
end

def save
  run_callbacks(:before_save)
  puts "- save"
  run_callbacks(:after_save)
end
end

config = ConfigStorage.new
config.save

Output:

saving...
- save
saved

Callbacks from parent classes are inherited.

Example:

class Storage
include ActiveSupport::Callbacks

define_callbacks :before_save, :after_save

before_save :prepare
def prepare
  puts "preparing save"
end
end

class ConfigStorage < Storage
before_save :saving_message
def saving_message
  puts "saving..."
end

after_save do |object|
  puts "saved"
end

def save
  run_callbacks(:before_save)
  puts "- save"
  run_callbacks(:after_save)
end
end

config = ConfigStorage.new
config.save

Output:

preparing save
saving...
- save
saved

Defined Under Namespace

Modules: ClassMethods Classes: Callback, CallbackChain

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.included(base) ⇒ Object 



200
201
202
 
# File 'lib/active_support/callbacks.rb', line 200

def self.included(base)
  base.extend ClassMethods
end

Instance Method Details

#run_callbacks(kind, options = {}, &block) ⇒ Object

Runs all the callbacks defined for the given options.

If a block is given it will be called after each callback receiving as arguments:

  • the result from the callback
  • the object which has the callback

If the result from the block evaluates to false, the callback chain is stopped.

Example:

class Storage
include ActiveSupport::Callbacks

define_callbacks :before_save, :after_save
end

class ConfigStorage < Storage
before_save :pass
before_save :pass
before_save :stop
before_save :pass

def pass
  puts "pass"
end

def stop
  puts "stop"
  return false
end

def save
  result = run_callbacks(:before_save) { |result, object| result == false }
  puts "- save" if result
end
end

config = ConfigStorage.new
config.save

Output:

pass
pass
stop


275
276
277
 
# File 'lib/active_support/callbacks.rb', line 275

def run_callbacks(kind, options = {}, &block)
  self.class.send("#{kind}_callback_chain").run(self, options, &block)
end