# How to set a relationship with a value from a selection list **URL:** \ **Category:** Rails\ **Created:** [February 23, 2006, 2:28pm UTC](https://www.ruby-forum.com/t/how-to-set-a-relationship-with-a-value-from-a-selection-list/72311 "2006-02-23T14:28:22Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![m3oliver](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b4bc9f/32.png) [@m3oliver](https://www.ruby-forum.com/u/m3oliver)\ **Post date:** [February 23, 2006, 2:28pm UTC](https://www.ruby-forum.com/t/how-to-set-a-relationship-with-a-value-from-a-selection-list/72311/1 "2006-02-23T14:28:22Z")
I realize this is probably a very basic problem but I’m developing my first rails app and running into this problem. I’m trying to write a photoblog application. I have a photo table and an album table. Photo has a to-one relationship to Album. Photo.album\_id =\> Album.id In my view for photo I have a selection list that’s populated with all the available albums. \<%= select(“post”, “album\_id”, Album.find\_all.collect {|a| [a.name, a.id]}, {:include\_blank =\> true}) %\> This work in so much as I can see the albums being listed in the selection list. Then in my photo\_controller I’m trying to set the relationship when the photo is saved in a method called ‘create’ def create @photo = Photo.new(params[:photo]) @photo\_file = PhotoFile.new(params[:photo\_file]) @photo.photo\_file = @photo\_file @photo.album = @post.album\_id @photo.blog\_user\_id = 1 if @photo.save! flash[:notice] = ‘Photo was successfully created.’ redirect\_to :action =\> ‘list’ else render :action =\> ‘new’ end end When I click save I get the following error… NoMethodError in Photo#create You have a nil object when you didn’t expect it! The error occured while evaluating nil.album\_id I’ve looked through this forum and read numerous similar problems, and from what I can tell I’m doing the right thing. Can someone tell me where I’m being thick. -Matt ---
**Author:** ![m3oliver](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b4bc9f/32.png) [@m3oliver](https://www.ruby-forum.com/u/m3oliver)\ **Post date:** [February 23, 2006, 3:22pm UTC](https://www.ruby-forum.com/t/how-to-set-a-relationship-with-a-value-from-a-selection-list/72311/2 "2006-02-23T15:22:40Z")
On Thu, Feb 23, 2006 at 02:28:22PM +0100, Matthew Oliver wrote: > I’m trying to write a photoblog application. I have a photo table and an > album table. Photo has a to-one relationship to Album. Photo.album\_id =\> > Album.id > > In my view for photo I have a selection list that’s populated with all > the available albums. > \<%= select(“post”, “album\_id”, Album.find\_all.collect {|a| [a.name, > a.id]}, {:include\_blank =\> true}) %\> s/post/photo/ > @photo.album = @post.album\_id > Remove this line because the hash params[:photo] will contain > the album\_id. > @photo.blog\_user\_id = 1 > if @photo.save! > flash[:notice] = ‘Photo was successfully created.’ > redirect\_to :action =\> ‘list’ > else > render :action =\> ‘new’ > end > end FWIW I’m new to rails so I could easily be way wrong with my suggestion. 🙂 -steve ---
**Author:** ![m3oliver](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b4bc9f/32.png) [@m3oliver](https://www.ruby-forum.com/u/m3oliver)\ **Post date:** [February 23, 2006, 4:04pm UTC](https://www.ruby-forum.com/t/how-to-set-a-relationship-with-a-value-from-a-selection-list/72311/3 "2006-02-23T16:04:33Z")
> > @photo.album = @post.album\_id > > Remove this line because the hash params[:photo] will contain > > the album\_id. > > > @photo.blog\_user\_id = 1 > > if @photo.save! > > flash[:notice] = ‘Photo was successfully created.’ > > redirect\_to :action =\> ‘list’ > > else > > render :action =\> ‘new’ > > end > > end > > FWIW I’m new to rails so I could easily be way wrong with my > suggestion. 🙂 > > -steve Hi Steve If I simply remove that line I get a forien key restraint error. Mysql::Error: #23000Cannot add or update a child row: a foreign key constraint fails (`photoblog_development/photos`, CONSTRAINT `photos_ibfk_1` FOREIGN KEY (`album_id`) REFERENCES `albums` (`id`)): INSERT INTO photos (`lens`, `mounting`, `title`, `album_id`, `photo_description`, `camera`, `iso`, `shutter`, `blog_user_id`, `camera_mode`, `added_on`, `shot_on`, `aperture`, `flash`) VALUES(’’, ‘’, ‘’, 0, ‘’, ‘’, ‘’, ‘’, 1, ‘’, NULL, NULL, ‘’, ‘’) How do I go about setting this relationship? ---
**Author:** ![m3oliver](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b4bc9f/32.png) [@m3oliver](https://www.ruby-forum.com/u/m3oliver)\ **Post date:** [February 23, 2006, 4:20pm UTC](https://www.ruby-forum.com/t/how-to-set-a-relationship-with-a-value-from-a-selection-list/72311/4 "2006-02-23T16:20:15Z")
On Thursday, February 23, 2006, at 3:14 PM, Andrew Otwell wrote: > > @photo.album = @post.album\_id > > > You have a nil object when you didn’t expect it! > > The error occured while evaluating nil.album\_id > > You use @post, but it’s not defined anywhere. That looks like what’s > causing the nomethod error. Whoops, I meant to write: “That looks like what’s causing the _nil object_ error.” ---
**Author:** ![m3oliver](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b4bc9f/32.png) [@m3oliver](https://www.ruby-forum.com/u/m3oliver)\ **Post date:** [February 23, 2006, 4:55pm UTC](https://www.ruby-forum.com/t/how-to-set-a-relationship-with-a-value-from-a-selection-list/72311/5 "2006-02-23T16:55:05Z")
Andrew Otwell wrote: > On Thursday, February 23, 2006, at 3:14 PM, Andrew Otwell wrote: > > > > @photo.album = @post.album\_id > > > > > You have a nil object when you didn’t expect it! > > > The error occured while evaluating nil.album\_id > > > > You use @post, but it’s not defined anywhere. That looks like what’s > > causing the nomethod error. > > Whoops, I meant to write: “That looks like what’s causing the _nil > object_ error.” Ahhhh I see… So using the variable name post in the select statement isn’t enough? \<%= select(“post”, “album\_id”, Album.find\_all.collect {|a| [a.name, a.id]}, {:include\_blank =\> true}) %\> I thought calling it post here would mean I could reference in my controllor as such. I’m still lost as to what I should do? When I try to save the new photo I get an exception page that shows me the information from the request… in that information I see the album “post”=\>{“album\_id”=\>“1”}} and it’s pointing at the correct id and everything I just don’t know how to reference that request object in my controllor to set the relationship!?! frustrating! ---
**Author:** ![m3oliver](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b4bc9f/32.png) [@m3oliver](https://www.ruby-forum.com/u/m3oliver)\ **Post date:** [February 23, 2006, 4:17pm UTC](https://www.ruby-forum.com/t/how-to-set-a-relationship-with-a-value-from-a-selection-list/72311/6 "2006-02-23T16:17:13Z")
> @photo.album = @post.album\_id > You have a nil object when you didn’t expect it! > The error occured while evaluating nil.album\_id You use @post, but it’s not defined anywhere. That looks like what’s causing the nomethod error. ---
**Author:** ![m3oliver](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b4bc9f/32.png) [@m3oliver](https://www.ruby-forum.com/u/m3oliver)\ **Post date:** [February 23, 2006, 4:56pm UTC](https://www.ruby-forum.com/t/how-to-set-a-relationship-with-a-value-from-a-selection-list/72311/7 "2006-02-23T16:56:50Z")
On Thu, Feb 23, 2006 at 04:04:33PM +0100, Matthew Oliver wrote: > How do I go about setting this relationship? You need to remove the line mentioned as well as make the other change (post -\> photo) in the call to the select method in your view. If you don’t then the album\_id doesn’t get stuffed in the params[:photo] hash which is what is causing the error above. As it originally stood the album\_id could only be obtained using params[:post][:album\_id]. Putting it in the photo attributes hash means it is supplied to Photo.new in the following line of your code: @photo = Photo.new(params[:photo]) This mitigates the need to later have to resort to this: @photo.album\_id = params[:post][:album\_id]; -steve ---
**Author:** ![m3oliver](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b4bc9f/32.png) [@m3oliver](https://www.ruby-forum.com/u/m3oliver)\ **Post date:** [February 23, 2006, 5:20pm UTC](https://www.ruby-forum.com/t/how-to-set-a-relationship-with-a-value-from-a-selection-list/72311/8 "2006-02-23T17:20:41Z")
Awesome! It worked! Thank you so much Steve. -M