# Relations problem **URL:** \ **Category:** Rails\ **Created:** [January 21, 2008, 2:15pm UTC](https://www.ruby-forum.com/t/relations-problem/126698 "2008-01-21T14:15:32Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![kaizerkaizer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/45deac/32.png) [@kaizerkaizer](https://www.ruby-forum.com/u/kaizerkaizer)\ **Post date:** [January 21, 2008, 2:15pm UTC](https://www.ruby-forum.com/t/relations-problem/126698/1 "2008-01-21T14:15:32Z")
I’m using Restful Authentication (which I hope some of you know), so I’m using that Users-table as my main table. Now, I’ve added a table called ‘Presentations’. I’ve also added a presentation\_id in my Users-table so the right user’s presentation can be found. In my User-model I’ve got a “belongs\_to :presentation” and in my Presentation-model “belongs\_to :user”. As long as I create/assign everything MANUALLY in the tables it works fine. Now, that’s kind of dull to do for every new user signing in (especially since the presentation page will render a “nil-crash” if I haven’t assigned the user a Presentation with som text before he/she logges in). I know that I need to do a create function somewhere, but I’m unsure where to put it, though I’m guessing in the UserController’s create. I want it to create a default text once (upon creation of the new user) so the user later on can edit his/her presentation (a feature I’ve allready implemented). my question: Where do I create this “create” function (to work with Restful Authentication)and any suggestions on how should it look/work? ---
**Author:** ![kaizerkaizer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/45deac/32.png) [@kaizerkaizer](https://www.ruby-forum.com/u/kaizerkaizer)\ **Post date:** [January 21, 2008, 2:52pm UTC](https://www.ruby-forum.com/t/relations-problem/126698/2 "2008-01-21T14:52:06Z")
On Jan 21, 2008 8:15 AM, Dag S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I’m using Restful Authentication (which I hope some of you know), so I’m > using that Users-table as my main table. > > Now, I’ve added a table called ‘Presentations’. > I’ve also added a presentation\_id in my Users-table so the right user’s > presentation can be found. In my User-model I’ve got a “belongs\_to > :presentation” and in my Presentation-model “belongs\_to :user”. Something’s wrong here. Presentation :belongs\_to user means that Presentation has a column called user\_id which ‘points to’ a User. You dont have this. And belongs\_to isn’t symmetrical, the other end needs a :has\_many, or :has\_one relationship. From what you started out saying there’s one presentation for each user, in which case the relations would be: User has\_one :presentation Presentation belongs\_to :user with user\_id field in the presentations table. That said, has\_one is almost never used like this, if there really is a fixed one-one relationship between presentations and users then they probably should be combined in one table. If, on the other hand, the situation is that the User can have multiple presentations then you might want something like: User has\_many :presentations has\_one :current\_presentation, :order =\> “updated\_at DESC” where the current\_presentation uses the magic updated\_at field to get the most recently modified presentation. – Rick DeNatale My blog on Ruby [http://talklikeaduck.denhaven2.com/](http://talklikeaduck.denhaven2.com/) ---
**Author:** ![kaizerkaizer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/45deac/32.png) [@kaizerkaizer](https://www.ruby-forum.com/u/kaizerkaizer)\ **Post date:** [January 21, 2008, 3:44pm UTC](https://www.ruby-forum.com/t/relations-problem/126698/3 "2008-01-21T15:44:23Z")
> From what you started out saying there’s one presentation for each > user, in which case the relations would be: > > User > has\_one :presentation > > Presentation > belongs\_to :user > > with user\_id field in the presentations table. Allright, well this at least did make the relations clearer, thanks Rick. Still I’m not very clear about how to create a new presentation with a default value as a new user gets created (especially since the datatype TEXT dosen’t allow default values)? ---
**Author:** ![kaizerkaizer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/45deac/32.png) [@kaizerkaizer](https://www.ruby-forum.com/u/kaizerkaizer)\ **Post date:** [January 22, 2008, 11:07am UTC](https://www.ruby-forum.com/t/relations-problem/126698/4 "2008-01-22T11:07:28Z")
@presentation = current\_user.presentation @presentation = current\_user.presentation.create unless @presentation Now, all it does is it returns nil (I hate nil, btw because it’s allways so “unexpected”). The error msg beeing ([http://localhost:3000/users](http://localhost:3000/users)): “You have a nil object when you didn’t expect it! You might have expected an instance of ActiveRecord::Base. The error occurred while evaluating nil.create” ActiveRecord::Base expected an instance…? ---
**Author:** ![kaizerkaizer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/45deac/32.png) [@kaizerkaizer](https://www.ruby-forum.com/u/kaizerkaizer)\ **Post date:** [January 22, 2008, 11:55am UTC](https://www.ruby-forum.com/t/relations-problem/126698/5 "2008-01-22T11:55:27Z")
2008/1/22, Dag S. : > @presentation = current\_user.presentation > @presentation = current\_user.presentation.create unless @presentation > > Now, all it does is it returns nil (I hate nil, btw because it’s allways > so “unexpected”). @presentation = current\_user.create\_presentation(…) – Jean-François. ---
**Author:** ![kaizerkaizer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/45deac/32.png) [@kaizerkaizer](https://www.ruby-forum.com/u/kaizerkaizer)\ **Post date:** [January 21, 2008, 4:53pm UTC](https://www.ruby-forum.com/t/relations-problem/126698/6 "2008-01-21T16:53:35Z")
Another thing I’ve tried is to created a new Presentation object to the current\_user with: @presentation = current\_user.Presentation.new @presentation.save! by placing it in the UserController in the class definition “create” (which already exists)but this only generates half of what I want to accomplish: new rows, but sadly enough only NULL in the columns. ---
**Author:** ![kaizerkaizer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/45deac/32.png) [@kaizerkaizer](https://www.ruby-forum.com/u/kaizerkaizer)\ **Post date:** [January 22, 2008, 12:19pm UTC](https://www.ruby-forum.com/t/relations-problem/126698/7 "2008-01-22T12:19:14Z")
Jean-François Trân wrote: > 2008/1/22, Dag S. : > > > @presentation = current\_user.presentation > > @presentation = current\_user.presentation.create unless @presentation > > > > Now, all it does is it returns nil (I hate nil, btw because it’s allways > > so “unexpected”). > > @presentation = current\_user.create\_presentation(…) > > – Jean-Fran�ois. Thank you, Fran?ois! saved my day