先对所有callback都定义一次（不含around）

（全部callback的名字可在ActiveRecord::Callbacks::CALLBACKS查到）

irb(main):001:0> callbacks = User.methods.select{|m| m =~ /before|after/ and m.to_s.count('_') == 1}
=> [:after_find, :after_touch, :before_save, :after_save, :before_create, :after_create, :before_update, :after_update, :before_destroy, :after_destroy, :after_initialize, :after_commit, :after_rollback, :before_commit, :before_validation, :after_validation]
irb(main):002:0> callbacks.each do |cb|
irb(main):003:1*   User.send cb, &-> *arg {
irb(main):004:2*     stack = caller.each_with_object [] do |frame, st|
irb(main):005:3*       st << frame unless st[-1] =~ /irb_binding/
irb(main):006:3>     end
irb(main):007:2>     stack = "\n   " + stack.join("\n   ")
irb(main):008:2>     puts "#{cb}:#{stack}"
irb(main):009:2>   }
irb(main):010:1> end
=> [:after_find, :after_touch, :before_save, :after_save, :before_create, :after_create, :before_update, :after_update, :before_destroy, :after_destroy, :after_initialize, :after_commit, :after_rollback, :before_commit, :before_validation, :after_validation]


试试new，可看到它会调用after_initialize

irb(main):011:0> u = User.new name: 'ken', password: '123'
after_initialize:
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `instance_exec'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `block in make_lambda'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:207:in `block in halting_and_conditional'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `block in call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `each'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_initialize_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/core.rb:322:in `initialize'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/inheritance.rb:65:in `new'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/inheritance.rb:65:in `new'
   (irb):11:in `irb_binding'
=> #<user id:="" nil,="" name:="" "ken",="" password_digest:="" "$2a$10$1n0qb0yysm5x37pmlzu4ceflo8byfsei7ovgedidkhz...",="" created_at:="" nil,="" updated_at:="" nil=""></user>


源码如下

# activerecord-5.0.2/lib/active_record/core.rb
def initialize(attributes = nil)
  self.class.define_attribute_methods
  @attributes = self.class._default_attributes.deep_dup

  init_internals
  initialize_internals_callback

  assign_attributes(attributes) if attributes

  yield self if block_given?
  _run_initialize_callbacks
end


而save相关的callback，顺序如下：before_validation，after_validation，before_save，before_create，after_create，after_save，before_commit，after_commit

irb(main):012:0> u.save
   (0.1ms)  begin transaction
before_validation:
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `instance_exec'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `block in make_lambda'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:169:in `block (2 levels) in halting'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:770:in `block (2 levels) in deprecated_false_terminator'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:769:in `catch'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:769:in `block in deprecated_false_terminator'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:170:in `block in halting'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `block in call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `each'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_validation_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activemodel-5.0.2/lib/active_model/validations/callbacks.rb:113:in `run_validations!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activemodel-5.0.2/lib/active_model/validations.rb:338:in `valid?'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/validations.rb:65:in `valid?'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/validations.rb:82:in `perform_validations'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/validations.rb:44:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/attribute_methods/dirty.rb:22:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block (2 levels) in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:395:in `block in with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `block in transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:189:in `within_new_transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:211:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:392:in `with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:334:in `rollback_active_record_state!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:318:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/suppressor.rb:41:in `save'
   (irb):12:in `irb_binding'
after_validation:
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `instance_exec'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `block in make_lambda'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:218:in `block in halting'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `block in call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `each'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_validation_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activemodel-5.0.2/lib/active_model/validations/callbacks.rb:113:in `run_validations!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activemodel-5.0.2/lib/active_model/validations.rb:338:in `valid?'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/validations.rb:65:in `valid?'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/validations.rb:82:in `perform_validations'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/validations.rb:44:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/attribute_methods/dirty.rb:22:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block (2 levels) in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:395:in `block in with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `block in transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:189:in `within_new_transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:211:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:392:in `with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:334:in `rollback_active_record_state!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:318:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/suppressor.rb:41:in `save'
   (irb):12:in `irb_binding'
before_save:
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `instance_exec'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `block in make_lambda'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:169:in `block (2 levels) in halting'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:770:in `block (2 levels) in deprecated_false_terminator'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:769:in `catch'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:769:in `block in deprecated_false_terminator'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:170:in `block in halting'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `block in call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `each'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_save_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/callbacks.rb:298:in `create_or_update'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/persistence.rb:125:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/validations.rb:44:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/attribute_methods/dirty.rb:22:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block (2 levels) in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:395:in `block in with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `block in transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:189:in `within_new_transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:211:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:392:in `with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:334:in `rollback_active_record_state!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:318:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/suppressor.rb:41:in `save'
   (irb):12:in `irb_binding'
before_create:
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `instance_exec'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `block in make_lambda'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:169:in `block (2 levels) in halting'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:770:in `block (2 levels) in deprecated_false_terminator'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:769:in `catch'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:769:in `block in deprecated_false_terminator'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:170:in `block in halting'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `block in call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `each'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_create_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/callbacks.rb:302:in `_create_record'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/timestamp.rb:68:in `_create_record'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/persistence.rb:540:in `create_or_update'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/callbacks.rb:298:in `block in create_or_update'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:126:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:506:in `block (2 levels) in compile'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:455:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_save_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/callbacks.rb:298:in `create_or_update'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/persistence.rb:125:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/validations.rb:44:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/attribute_methods/dirty.rb:22:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block (2 levels) in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:395:in `block in with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `block in transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:189:in `within_new_transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:211:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:392:in `with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:334:in `rollback_active_record_state!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:318:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/suppressor.rb:41:in `save'
   (irb):12:in `irb_binding'
  SQL (0.5ms)  INSERT INTO "users" ("name", "password_digest", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["name", "ken"], ["password_digest", "$2a$10$1N0qb0YySm5X37pMLzu4CeFlo8BYFSEi7OVgeDIdKhZlLfE6lTbf2"], ["created_at", 2017-05-01 04:49:18 UTC], ["updated_at", 2017-05-01 04:49:18 UTC]]
after_create:
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `instance_exec'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `block in make_lambda'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:207:in `block in halting_and_conditional'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `block in call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `each'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_create_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/callbacks.rb:302:in `_create_record'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/timestamp.rb:68:in `_create_record'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/persistence.rb:540:in `create_or_update'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/callbacks.rb:298:in `block in create_or_update'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:126:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:506:in `block (2 levels) in compile'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:455:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_save_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/callbacks.rb:298:in `create_or_update'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/persistence.rb:125:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/validations.rb:44:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/attribute_methods/dirty.rb:22:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block (2 levels) in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:395:in `block in with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `block in transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:189:in `within_new_transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:211:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:392:in `with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:334:in `rollback_active_record_state!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:318:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/suppressor.rb:41:in `save'
   (irb):12:in `irb_binding'
after_save:
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `instance_exec'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `block in make_lambda'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:207:in `block in halting_and_conditional'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `block in call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `each'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_save_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/callbacks.rb:298:in `create_or_update'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/persistence.rb:125:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/validations.rb:44:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/attribute_methods/dirty.rb:22:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block (2 levels) in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:395:in `block in with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `block in transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:189:in `within_new_transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:211:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:392:in `with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:334:in `rollback_active_record_state!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:318:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/suppressor.rb:41:in `save'
   (irb):12:in `irb_binding'
before_commit:
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `instance_exec'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `block in make_lambda'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:169:in `block (2 levels) in halting'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:770:in `block (2 levels) in deprecated_false_terminator'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:769:in `catch'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:769:in `block in deprecated_false_terminator'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:170:in `block in halting'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `block in call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `each'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:454:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_before_commit_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:344:in `before_committed!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:80:in `each'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:80:in `before_commit_records'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:172:in `commit_transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:202:in `within_new_transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:211:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:392:in `with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:334:in `rollback_active_record_state!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:318:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/suppressor.rb:41:in `save'
   (irb):12:in `irb_binding'
   (2.3ms)  commit transaction
after_commit:
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `instance_exec'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:396:in `block in make_lambda'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:242:in `block in simple'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `block in call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `each'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:456:in `call'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activesupport-5.0.2/lib/active_support/callbacks.rb:750:in `_run_commit_callbacks'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:354:in `committed!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:87:in `commit_records'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:178:in `commit_transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/transaction.rb:202:in `within_new_transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:211:in `transaction'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:392:in `with_transaction_returning_status'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:319:in `block in save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:334:in `rollback_active_record_state!'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/transactions.rb:318:in `save'
   /home/z/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/activerecord-5.0.2/lib/active_record/suppressor.rb:41:in `save'
   (irb):12:in `irb_binding'
=> true


其它find、update、destroy也可由此检查，其结果会是如下


真去查看源码的话，会发现_run_xxx_callbacks都是写死的（约定的），因为active_support/callback所生成的callback方法就是这种命名规则