Why isn't ActiveRecord's autosave working on my association?

callback, rails-activerecord, ruby, ruby-on-rails

Solution

The problem here is that `autosave: true` simply sets up a normal `before_save` callback, and `before_save` callbacks are run in the order that they're created.**

Therefore, it tries to save the `bar`, which has no changes, then it calls `modify_bar`.

The solution is to ensure that the `modify_bar` callback runs before the autosave.

One way to do that is with the `prepend` option.

class Foo
  belongs_to :bar, autosave: true
  before_save :modify_bar, prepend: true
  ...
end

Another way would be to put the `before_save` statement before the `belongs_to`.

Another way would be to explicitly save `bar` at the end of the `modify_bar` method and not use the `autosave` option at all.

Thanks to Danny Burkes for the helpful blog post.

** Also, they're run after all `after_validation` callbacks and before any `before_create` callbacks - see the docs.

Update

Here's one way to check the order of such callbacks.

  describe "sequence of callbacks" do

    let(:sequence_checker) { SequenceChecker.new }

    before :each do
      foo.stub(:bar).and_return(sequence_checker)
    end

    it "modifies bar before saving it" do
      # Run the before_save callbacks and halt before actually saving
      foo.run_callbacks(:save) { false }
      # Test one of the following
      #
      # If only these methods should have been called
      expect(sequence_checker.called_methods).to eq(%w[modify save])
      # If there may be other methods called in between
      expect(sequence_checker.received_in_order?('modify', 'save')).to be_true
    end

  end

Using this supporting class:

class SequenceChecker
  attr_accessor :called_methods

  def initialize
    self.called_methods = []
  end

  def method_missing(method_name, *args)
    called_methods << method_name.to_s
  end

  def received_in_order?(*expected_methods)
    expected_methods.map!(&:to_s)
    called_methods & expected_methods == expected_methods
  end

end

Problem

Original source