What is the order of ActiveRecord callbacks and validations?
Ruby on-RailsRuby on-Rails-3ValidationActiverecordRuby on-Rails Problem Overview
I was wondering in what order are callbacks and validations called when an ActiveRecord object is created.
Let’s say I have some custom validations & callbacks like the following:
validates :reference_code, :if => :reference_code, :on => :create
before_create :assign_reference
which one will run first? The callback needs to happen first or else the validation may fail.
Ruby on-Rails Solutions
Solution 1 - Ruby on-Rails
The most-up-to-date version of this list for the latest version of Rails can be found in the ActiveRecord::Callbacks documentation. The lists for Rails 4, 3 & 2 are below.
Rails 4
The most up-to-date version of this list can be found in the Rails 4 Guides.
Creating an object
before_validationafter_validationbefore_savearound_savebefore_createaround_createafter_createafter_saveafter_commit/after_rollback
Updating an object
before_validationafter_validationbefore_savearound_savebefore_updatearound_updateafter_updateafter_saveafter_commit/after_rollback
Destroying an object
before_destroyaround_destroyafter_destroyafter_commit/after_rollback
Rails 3
The most up-to-date version of this list can be found in the Rails 3 Guides.
Creating an object
before_validationafter_validationbefore_savearound_savebefore_createaround_createafter_createafter_save
Updating an object
before_validationafter_validationbefore_savearound_savebefore_updatearound_updateafter_updateafter_save
Destroying an object
before_destroyaround_destroyafter_destroy
Rails 2
The most up-to-date version of this list can be found in the Rails 2.3 Guides
Creating an object
before_validationbefore_validation_on_createafter_validationafter_validation_on_createbefore_savebefore_createINSERToperationafter_createafter_save
Updating an object
before_validationbefore_validation_on_updateafter_validationafter_validation_on_updatebefore_savebefore_updateUPDATEoperationafter_updateafter_save
Destroying an object
before_destroyDELETEoperationafter_destroy
Since you need to first validate the reference_code, the assign_reference method can be called in the after_validation callback or any callback appearing after it in the list I provided above.
Solution 2 - Ruby on-Rails
Rails 5
Here is a list with all the available Active Record callbacks, listed in the same order in which they will get called during the respective operations:
1 Creating an Object
before_validationafter_validationbefore_savearound_savebefore_createaround_createafter_createafter_saveafter_commit/after_rollback
2 Updating an Object
before_validationafter_validationbefore_savearound_savebefore_updatearound_updateafter_updateafter_saveafter_commit/after_rollback
3 Destroying an Object
before_destroyaround_destroyafter_destroyafter_commit/after_rollback
after_save runs both on create and update, but always after the more specific callbacks after_create and after_update, no matter the order in which the macro calls were executed.
before_destroy callbacks should be placed before dependent: :destroy associations (or use the prepend: true option), to ensure they execute before the records are deleted by dependent: :destroy.
Solution 3 - Ruby on-Rails
In addition to knowing the order each type of callback is called relative to the others, it's also important to be aware of the execution order of multiple callbacks of the same type. before_* hooks are executed in the order in which you define them, but after_* hooks are executed in reverse order. This can be surprising if you don't know it.