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add #no_touching on ActiveRecord models

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1 parent bba8bb8 commit b32ba367f584a6298fb8b7eef97be15388b5bd87 @dmathieu dmathieu committed Nov 5, 2013
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@@ -1,3 +1,13 @@
+* Added `ActiveRecord::Base.no_touching`, which allows ignoring touch on models.
+
+ Examples:
+
+ Post.no_touching do
+ Post.first.touch
+ end
+
+ *Sam Stephenson*, *Damien Mathieu*
+
* Prevent the counter cache from being decremented twice when destroying
a record on a has_many :through association.
@@ -45,6 +45,7 @@ module ActiveRecord
autoload :Migrator, 'active_record/migration'
autoload :ModelSchema
autoload :NestedAttributes
+ autoload :NoTouching
autoload :Persistence
autoload :QueryCache
autoload :Querying
@@ -295,6 +295,7 @@ class Base
extend Delegation::DelegateCache
include Persistence
+ include NoTouching
include ReadonlyAttributes
include ModelSchema
include Inheritance
@@ -0,0 +1,52 @@
+module ActiveRecord
+ # = Active Record No Touching
+ module NoTouching
+ extend ActiveSupport::Concern
+
+ module ClassMethods
+ # Lets you selectively disable calls to `touch` for the
+ # duration of a block.
+ #
+ # ==== Examples
+ # ActiveRecord::Base.no_touching do
+ # Project.first.touch # does nothing
+ # Message.first.touch # does nothing
+ # end
+ #
+ # Project.no_touching do
+ # Project.first.touch # does nothing
+ # Message.first.touch # works, but does not touch the associated project
+ # end
+ #
+ def no_touching(&block)
+ NoTouching.apply_to(self, &block)
+ end
+ end
+
+ class << self
+ def apply_to(klass) #:nodoc:
+ klasses.push(klass)
+ yield
+ ensure
+ klasses.pop
+ end
+
+ def applied_to?(klass) #:nodoc:
+ klasses.any? { |k| k >= klass }
+ end
+
+ private
+ def klasses
+ Thread.current[:no_touching_classes] ||= []
+ end
+ end
+
+ def no_touching?
+ NoTouching.applied_to?(self.class)
+ end
+
+ def touch(*)
+ super unless no_touching?
+ end
+ end
+end
@@ -11,6 +11,7 @@ class TimestampTest < ActiveRecord::TestCase
def setup
@developer = Developer.first
+ @owner = Owner.first
@developer.update_columns(updated_at: Time.now.prev_month)
@previously_updated_at = @developer.updated_at
end
@@ -92,6 +93,53 @@ def test_touching_a_record_without_timestamps_is_unexceptional
assert_nothing_raised { Car.first.touch }
end
+ def test_touching_a_no_touching_object
+ Developer.no_touching do
+ assert @developer.no_touching?
+ assert !@owner.no_touching?
+ @developer.touch
+ end
+
+ assert !@developer.no_touching?
+ assert !@owner.no_touching?
+ assert_equal @previously_updated_at, @developer.updated_at
+ end
+
+ def test_touching_related_objects
+ @owner = Owner.first
+ @previously_updated_at = @owner.updated_at
+
+ Owner.no_touching do
+ @owner.pets.first.touch
+ end
+
+ assert_equal @previously_updated_at, @owner.updated_at
+ end
+
+ def test_global_no_touching
+ ActiveRecord::Base.no_touching do
+ assert @developer.no_touching?
+ assert @owner.no_touching?
+ @developer.touch
+ end
+
+ assert !@developer.no_touching?
+ assert !@owner.no_touching?
+ assert_equal @previously_updated_at, @developer.updated_at
+ end
+
+ def test_no_touching_threadsafe
+ Thread.new do
+ Developer.no_touching do
+ assert @developer.no_touching?
+
+ sleep(1)
+ end
+ end
+
+ assert !@developer.no_touching?
+ end
+
def test_saving_a_record_with_a_belongs_to_that_specifies_touching_the_parent_should_update_the_parent_updated_at
pet = Pet.first
owner = pet.owner

7 comments on commit b32ba36

Member

Contributor

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Contributor

@dmathieu Could you give an example of a use case for this? I guess it could come in handy, but I can't come up with an example from the top of my head. 😊

Contributor

@fphilipe: this was a feature request coming from @dhh. I don't have a personal use case for it, I just did the implementation.
He says, as a use case:

Useful when copying object graphs while preserving the original timestamps, for example.

Contributor

@dmathieu OK, thanks!

Owner
dhh replied Nov 14, 2013

Here are two use cases from Basecamp:

def create_taggings_from_mass_assignment
  if @tag_names
    # Normally, tagging a taggable touches the taggable to expire
    # its caches. We can skip the touches here since we're in an
    # after_create callback and we know there are no caches to
    # expire. (Skipping these touches also lets us preserve the
    # original timestamps when copying messages and uploads with
    # tagged attachments.)

    ActiveRecord::Base.no_touching do
      set_tag_names(@tag_names)
    end

    @tag_names = nil
  end
end
class Copier
  def initialize(source, account)
    @source, @account = source, account
  end

  def copy
    ActiveRecord::Base.no_touching do
      @creator = find_person || create_person
      @project = create_project

      copy_todolists
      copy_messages
      copy_documents

      @project.reset_counters
      @project
    end
  rescue
    @project.try(:destroy)
    raise
  ensure
    @creator.try(:trash)
  end
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