# Newbie question **URL:** \ **Category:** Rails\ **Created:** [February 13, 2009, 7:22pm UTC](https://www.ruby-forum.com/t/newbie-question/160288 "2009-02-13T19:22:12Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![burrowsm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/d78d45/32.png) [@burrowsm](https://www.ruby-forum.com/u/burrowsm)\ **Post date:** [February 13, 2009, 7:22pm UTC](https://www.ruby-forum.com/t/newbie-question/160288/1 "2009-02-13T19:22:12Z")
Hey all, I’ve been working with rails for a grand total of 8 hours, and have run up against the first problem I haven’t been able to adequately solve using google. So I’ve got a schema that basically consists of a bunch of researchers. Each researcher has only one notebook. I’m trying to ensure that only one notebook can be created for each user. Below is the code I’ve been using in the create method for my notebook: existingbook = Notebook.find(:first, params[:researcher\_id]) @notebook = Notebook.new(params[:notebook]) ``` respond_to do |format| if (existingbook.nil?) if @notebook.save flash[:notice] = 'Notebook was successfully created.' format.html { redirect_to(@notebook) } format.xml { render :xml => @notebook, :status => :created, ``` :location =\> @notebook } else format.html { render :action =\> “new” } format.xml { render :xml =\> @notebook.errors, :status =\> :unprocessable\_entity } end else flash[:error] = ‘A notebook already exists for this user’ format.html { render :action =\> “new” } format.xml { render :xml =\> @notebook.errors, :status =\> :unprocessable\_entity } end end The basic idea is to check the notebook table for the researcher id specified by the user. If a notebook already exists, send an error message back. Otherwise, create the notebook as usual. However, the above code doesn’t work like I think it should. Basically what I have above always allows another notebook to be created (e.g. I can enter researcher\_id of 1 five times in a row without an error). Is there something I’m missing? Is there any way to check the database to see if a value exists already before saving it off? I’m probably missing something simple here, and if anyone has some input I would greatly appreciate the assistance. ---
**Author:** ![burrowsm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/d78d45/32.png) [@burrowsm](https://www.ruby-forum.com/u/burrowsm)\ **Post date:** [February 13, 2009, 8:07pm UTC](https://www.ruby-forum.com/t/newbie-question/160288/2 "2009-02-13T20:07:24Z")
On 13 Feb 2009, at 18:22, Matt Billock wrote: > Each researcher has only one notebook. I’m trying to ensure that only > one notebook can be created for each user. Below is the code I’ve been > using in the create method for my notebook: > > existingbook = Notebook.find(:first, params[:researcher\_id]) This doesn’t find a notebook with the specified researcher\_id. It just finds a notebook (and thinking about it, how could Notebook.find know that the parameter you were giving it was a researched\_id and not something else?\_ If you check log/development.log while you’re doing this you can see the sql queries generated which would reveal this. What you probably meant to write is Notebook.find\_by\_researcher\_id(params[:researcher\_id]) or if you wanted to be long winded Notebook.find :first, :conditions =\> [“researcher\_id = ?”, params[:researcher\_id]] Lastly, take a look at validates\_uniqueness\_of and be aware of the race condition inherent in the way it works (your code suffers from the same problem) Fred ---
**Author:** ![burrowsm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/d78d45/32.png) [@burrowsm](https://www.ruby-forum.com/u/burrowsm)\ **Post date:** [February 13, 2009, 8:30pm UTC](https://www.ruby-forum.com/t/newbie-question/160288/3 "2009-02-13T20:30:41Z")
Frederick C. wrote: > On 13 Feb 2009, at 18:22, Matt Billock wrote: > > This doesn’t find a notebook with the specified researcher\_id. It just > finds a notebook (and thinking about it, how could Notebook.find know > that the parameter you were giving it was a researched\_id and not > something else?\_ > > If you check log/development.log while you’re doing this you can see > the sql queries generated which would reveal this. > > What you probably meant to write is > Notebook.find\_by\_researcher\_id(params[:researcher\_id]) or if you > wanted to be long winded > > Notebook.find :first, :conditions =\> [“researcher\_id = ?”, > params[:researcher\_id]] > > Lastly, take a look at validates\_uniqueness\_of and be aware of the > race condition inherent in the way it works (your code suffers from > the same problem) > > Fred Thanks much for the reply! I figured it was something simple like that. I just implemented the validates\_uniqueness\_of attribute before coming back here and it does the job much better than I could 🙂 ---
**Author:** ![burrowsm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/d78d45/32.png) [@burrowsm](https://www.ruby-forum.com/u/burrowsm)\ **Post date:** [February 14, 2009, 6:25am UTC](https://www.ruby-forum.com/t/newbie-question/160288/4 "2009-02-14T06:25:38Z")
Hey man. Welcome! First thing, from hereonin, please put more meaningful subject names. We get lots of noob questions. Second, what you’d like is belongs\_to association. Take a look in activerecord::base documentation at [api.rubyonrails.org](http://api.rubyonrails.org) Blog: [http://random8.zenunit.com/](http://random8.zenunit.com/) Learn rails: [http://sensei.zenunit.com/](http://sensei.zenunit.com/) On 14/02/2009, at 5:22 AM, Matt Billock \ **Author:** ![burrowsm](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/d78d45/32.png) [@burrowsm](https://www.ruby-forum.com/u/burrowsm)\ **Post date:** [February 14, 2009, 11:13am UTC](https://www.ruby-forum.com/t/newbie-question/160288/5 "2009-02-14T11:13:32Z") Create a unique index for the foreign key (user\_id) in the notebook table!