# How to write manage created\_on and created\_by via mixin?

**URL:** <https://www.ruby-forum.com/t/how-to-write-manage-created-on-and-created-by-via-mixin/87369>\
**Category:** Rails\
**Created:** [March 26, 2006, 9:38pm UTC](https://www.ruby-forum.com/t/how-to-write-manage-created-on-and-created-by-via-mixin/87369 "2006-03-26T21:38:08Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![Rob\_Greene](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/b2d939/32.png) [@Rob\_Greene](https://www.ruby-forum.com/u/Rob_Greene)\
**Post date:** [March 26, 2006, 9:38pm UTC](https://www.ruby-forum.com/t/how-to-write-manage-created-on-and-created-by-via-mixin/87369/1 "2006-03-26T21:38:08Z")

</div>

Hi!

Definite newbie here - I’m working through this like-hate relationship  
with  
Ruby and Rails right now… sometimes things work really well (like  
blobs  
seem to rock) but other times, I dunno! 🙂

Anyway, I’d like put in create and update user timestamps on all my  
primary  
domain tables and allow them to be updated automatically by  
ActiveRecord.  
Coming from Hibernate, I just place an interceptor that dynamically  
discovers the column names and sets it up. In Ruby, I’m totally lost.  
However, I hold out hope - I just don’t know the terminology for what  
I’m  
looking for since what I’m doing has to be relatively common.

So, I’ve created a mixin called UserTimestamp.rb:  
module UserTimestamp  
def mark\_created  
self.created\_on = Time.new  
self.created\_by = @user.user\_id  
end

def mark\_updated  
self.updated\_on = Time.new  
self.updated\_by = @user.user\_id  
end  
end

And, then I include it and setup the before\_create and after\_create  
macros:  
require ‘lib/UserTimestamp.rb’

class Video \< ActiveRecord::Base  
include UserTimestamp  
before\_create :mark\_created  
before\_update :mark\_updated

# … etc…

end

Of course, this doesn’t work, but that seemed logical. Neither @user or  
user  
is present, nor do I have any way to get the user\_id. User is identified  
in  
my ApplicationController by a filter which is available in all my  
controllers. However, I have absolutely no way of locating the User  
object  
from an ActiveRecord class… or do I? Do I need to pass it in on create  
or  
something weird like that? (Or, yuck, manually invoke it??)

Is there a better way to do this? This does work, but I wonder if  
there’s a  
more appropriate manner.

Thanks for any feedback!  
-Rob

---

<div class="post-metadata">

**Author:** ![Rob\_Greene](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/b2d939/32.png) [@Rob\_Greene](https://www.ruby-forum.com/u/Rob_Greene)\
**Post date:** [March 26, 2006, 9:58pm UTC](https://www.ruby-forum.com/t/how-to-write-manage-created-on-and-created-by-via-mixin/87369/2 "2006-03-26T21:58:51Z")

</div>

Heh… you’re gonna laugh… or cry…

[http://wiki.rubyonrails.com/rails/pages/MagicFieldNames](http://wiki.rubyonrails.com/rails/pages/MagicFieldNames)

(also pg 277 in AWDWR)

It’s all done for ya baby… I’m finding that any time I think of a  
cool thing to do in  
rails, it’s already been done.

b

---

<div class="post-metadata">

**Author:** ![Rob\_Greene](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/b2d939/32.png) [@Rob\_Greene](https://www.ruby-forum.com/u/Rob_Greene)\
**Post date:** [March 27, 2006, 2:53am UTC](https://www.ruby-forum.com/t/how-to-write-manage-created-on-and-created-by-via-mixin/87369/3 "2006-03-27T02:53:02Z")

</div>

Hey, excellent! I’m actually close to going down the right path?! (Ok,  
well  
the timestamps will take care of themself…)

Anyway, I chased down the user-level information to this post:

[http://livsey.org/2005/07/16/adding\_created\_by\_and\_updated\_by\_to\_rails/](http://livsey.org/2005/07/16/adding_created_by_and_updated_by_to_rails/)

The current\_user is simply stored in a class-level attribute on User  
which,  
in turn, is set by a before\_filter on the application controller. Neat  
an  
nifty… except - that’s not thread safe, right?? If two people hit the  
site at the same time, User.current\_user holds the last one, and all  
record  
updates will be attributed to that person. (Maybe I’m thinking too much  
like  
a Java person here…)

-Rob

---

<div class="post-metadata">

**Author:** ![Rob\_Greene](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/b2d939/32.png) [@Rob\_Greene](https://www.ruby-forum.com/u/Rob_Greene)\
**Post date:** [March 27, 2006, 3:59am UTC](https://www.ruby-forum.com/t/how-to-write-manage-created-on-and-created-by-via-mixin/87369/4 "2006-03-27T03:59:07Z")

</div>

rails is process-based, not thread based. There are no issues with  
multi-threading because each process handles 1 request.

---

<div class="post-metadata">

**Author:** ![Rob\_Greene](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/b2d939/32.png) [@Rob\_Greene](https://www.ruby-forum.com/u/Rob_Greene)\
**Post date:** [March 27, 2006, 4:07am UTC](https://www.ruby-forum.com/t/how-to-write-manage-created-on-and-created-by-via-mixin/87369/5 "2006-03-27T04:07:20Z")

</div>

Rob Greene wrote:  
[…]

> Anyway, I chased down the user-level information to this post:
> 
> [http://livsey.org/2005/07/16/adding\_created\_by\_and\_updated\_by\_to\_rails/](http://livsey.org/2005/07/16/adding_created_by_and_updated_by_to_rails/)
> 
> The current\_user is simply stored in a class-level attribute on User  
> which, in turn, is set by a before\_filter on the application controller.  
> Neat an nifty… except - that’s not thread safe, right?? If two people  
> hit the site at the same time, User.current\_user holds the last one, and  
> all record updates will be attributed to that person. (Maybe I’m  
> thinking too much like a Java person here…)

Yes, you would be right if Rails worked like Java servlets.

Rails is single-threaded (at least for the moment), so the approach of  
using a model class variable is safe. In Rails running under Webrick,  
only one request is processed at a time.

In production envvironments there may be multiple FastCGI (or SCGI)  
processes, but each process only handles one request at a time. It  
would be quite possible for multiple users’ requests to be handled  
concurrently, but in separate processes, each with its own User class  
and current\_user class variable.

regards

Justin

---

<div class="post-metadata">

**Author:** ![Rob\_Greene](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/b2d939/32.png) [@Rob\_Greene](https://www.ruby-forum.com/u/Rob_Greene)\
**Post date:** [March 27, 2006, 4:52am UTC](https://www.ruby-forum.com/t/how-to-write-manage-created-on-and-created-by-via-mixin/87369/6 "2006-03-27T04:52:11Z")

</div>

Wow, what a concept! That opens up a few doors I wouldn’t otherwise  
consider…

Thanks!  
-Rob