updates - Rails: update_column works, but not update_attributes

Question

I have a simple model:

class Reply < ActiveRecord::Base
  attr_accessible :body
  belongs_to :post
end

In my controller, I have a simple update method:

def update
  @reply = Reply.find(params[:id])
  if @reply.update_attributes!(params[:reply])
    render :js => "alert('I am trying to update!')"
  else
    render :js => "alert('<%= @reply.errors %>')"
  end
end

This doesn't throw an error, but neither does it actually update the reply. Instead, I get the "I am trying to update!" message, like everything worked. But when I reload the page and look at the reply, it has the same text. It hasn't actually been updated. If I replace update_attributes with:

@reply.update_column(:body, params[:reply][:body])

It works fine. If I use:

@reply.update_attribute(:body, params[:reply][:body])

It once again doesn't work. Any idea what's going?

In my log, I have this:

Started PUT "/posts/2/replies/20" for 127.0.0.1 at 2013-01-19 10:39:57 -0600
Processing by RepliesController#update as JS
Parameters: {"utf8"=>"?", "authenticity_token"=>"Xot7E+ldXiBm0hVvw5XUP/U5guJU2g8e4QaLbDVGzDE=", "reply"=>{"body"=>"Updated text."}, "commit"=>"Submit Revision", "post_id"=>"2", "id"=>"20"
[1m[35mUser Load (1.0ms)[0m  SELECT `users`.* FROM `users` WHERE `users`.`id` = 1 LIMIT 1
[1m[36mReply Load (0.0ms)[0m  [1mSELECT `replies`.* FROM `replies` WHERE `replies`.`id` = 20 LIMIT 1[0m
[1m[35m (1.0ms)[0m  BEGIN
[1m[36mPost Load (0.0ms)[0m  [1mSELECT `posts`.* FROM `posts` WHERE `posts`.`id` = 2 LIMIT 1[0m
[1m[35m (0.0ms)[0m  COMMIT
Rendered replies/_reply_content.html.erb (502.0ms)
Rendered replies/update.js.erb (505.0ms)
Completed 200 OK in 849ms (Views: 484.0ms | ActiveRecord: 94.0ms)

Answer 1

The three methods you are using do different things:

• update_attributes tries to validate the record, calls callbacks and saves;
• update_attribute doesn't validate the record, calls callbacks and saves;
• update_column doesn't validate the record, doesn't call callbacks, doesn't call save method, though it does update record in the database.

If the only method that "works" is update_column my guess is that you have a callback somewhere that is throwing an error. Try to check your log/development.log file to see what's going on.

You can also use update_attributes!. This variant will throw an error, so it may give you information on why your model isn't saving.

You should use update_attributes and avoid the two other methods unless you know exactly what you are doing. If you add validations and callbacks later to your model, using update_attribute and update_column can lead to nasty behaviour that is really difficult to debug.

You can check this link for more info on that.