Skipping :touch associations when saving an ActiveRecord object

Question

Is there a way to skip updating associations with a :touch association when saving?

Setup:

class School < ActiveRecord::Base
  has_many :students
end

class Student < ActiveRecord::Base
  belongs_to :school, touch: true
end

I would like to be able to do something like the following where the touch is skipped.

@school = School.create
@student = Student.create(school_id: @school.id)
@student.name = "Trevor"
@student.save # Can I do this without touching the @school record?

Can you do this? Something like @student.save(skip_touch: true) would be fantastic but I haven't found anything like that.

I don't want to use something like update_column because I don't want to skip the AR callbacks.

Answer 1

As of Rails v4.1.0.beta1, the proper way to do this would be:

@school = School.create
@student = Student.create(school_id: @school.id)

ActiveRecord::Base.no_touching do
  @student.name = "Trevor"
  @student.save
end

Answer 2

One option that avoids directly monkey patching is to override the method that gets created when you have a relation with a :touch attribute.

Given the setup from the OP:

class Student < ActiveRecord::Base
  belongs_to :school, touch: true

  attr_accessor :skip_touch

  def belongs_to_touch_after_save_or_destroy_for_school
    super unless skip_touch
  end

  after_commit :reset_skip_touch

  def reset_skip_touch
    skip_touch = false
  end
end

@student.skip_touch = true
@student.save # touch will be skipped for this save

This is obviously pretty hacky and depends on really specific internal implementation details in AR.

Answer 3

Unfortunately, no. save doesn't provide such option.

Work around this would be to have another time stamp attribute that functions like updated_at but unlike updated_at, it updates only on certain situations for your liking.