Why does after_save not trigger when using touch?

Question

Recent days , I was trying to cache rails app use Redis store. I have two models:

class Category < ActiveRecord::Base
  has_many :products

  after_save :clear_redis_cache

  private

    def clear_redis_cache
      puts "heelllooooo"
      $redis.del 'products'
    end
end

and

class Product < ActiveRecord::Base
  belongs_to :category, touch: true
end

in controller

def index
    @products = $redis.get('products')

    if @products.nil?
      @products = Product.joins(:category).pluck("products.id", "products.name", "categories.name")
      $redis.set('products', @products)
      $redis.expire('products', 3.hour.to_i)
    end

    @products = JSON.load(@products) if @products.is_a?(String)

  end

With this code , the cache worked fine. But when I updated or created new product (I have used touch method in relationship) it's not trigger after_save callback in Category model. Can you explain me why ?

Solution 1

Have you read documentation for touch method?

Saves the record with the updated_at/on attributes set to the current time. Please note that no validation is performed and only the after_touch, after_commit and after_rollback callbacks are executed. If an attribute name is passed, that attribute is updated along with updated_at/on attributes.

Solution 2

If you want after_save callbacks to be executed when calling touch on some model, you can add

after_touch :save

to this model.

Solution 3

If you set the :touch option to :true, then the updated_at or updated_on timestamp on the associated object will be set to the current time whenever this object is saved or destroyed this the doc : http://guides.rubyonrails.org/association_basics.html#touch

Comments

[Oleg Afanasyev]

If all you need is just to trigger after_save callbacks please use save method.

[Ken Ratanachai S.]

How does this work? :save is a special word for callbacks?

[Aymeric Bouzy aybbyk]

it triggers the save method after each touch, which will be a no-op, which will in turn trigger the after_save callbacks (from what I understood, I'm no expert)