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Difference between before_save and before_update and before_create in Rails

When defining ActiveRecord callbacks I’ve sometimes needed to ask myself “should I use before_save here or before_create“ and when coming to the answer for this question there are also implications for when to use before_update.

Ultimately if you only need the callback to be invoked when the record is first created, use before_create. If you need the callback to be invoked every time the record is updated you can use the before_update callback. And if you need the ballback invoked when the object is both created and updated you would use the before_save callback method.

As with all ActiveRecord public instance methods you will also have access to the object within the invoked callback method, it can be referenced explicitly through self. Or you can just call its attribute methods directly because self is the default object.

class Account < ApplicationRecord
  before_save :clean_record

  def clean_record
    p "#{self.inspect}"
    p "#{name}"

Accout.create(name: "blue bacon", email: "blue@bacon.istasty")
# Puts output from clean_record invocation:
# "#<Account id: nil, name: \"blue bacon\", email: \"blue@bacon.istasty\", admin: nil, created_at: nil, updated_at: nil>"
# "blue bacon"

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