Hi, I'm on winXP, learning to use RoR to talk with MySQL. I'm tweaking the .rhtml code in views to change the default look of the "edit" and "new" pages. I changed the edit.rhtml page so that I get a list of records in addition to the record editing form. I merely copy-pasted the code from the list.rhtml page for this. I get a "nil object" error. If I remove the code that actually lists the entries and only have the code that writes the column headings everything goes fine. Is this a ruby bug? thanks!
on 2005-11-26 08:26
on 2005-11-26 08:38
I haven't used scaffolding much but here is my guess. In the list action it probably has something like def list @items = Items.find(:all) end Copy and paste this line to your edit action so that the items are available in the view. -Peter
on 2005-11-26 17:15
Hi Peter, Thanks for your reply. I don't know if I need that. Here is the code #copied verbatim from list.rhtml <table> <tr> <% for column in Note.content_columns %> <th><%= column.human_name %></th> <% end %> </tr> #This part works just fine <% for note in @notes %> <tr> <% for column in Note.content_columns %> <td><%=h note.send(column.name) %></td> <% end %> </tr> <% end %> #This part screws up </table> #left unchanged for edit.rhtml <h1>Editing note <%=@note.title%></h1> <%= start_form_tag :action => 'update', :id => @note %> <%= render :partial => 'form' %> <%= submit_tag 'Edit' %> <%= end_form_tag %> <%= link_to 'Show', :action => 'show', :id => @note %> | <%= link_to 'Back', :action => 'list' %> So there is indeed an iterator over notes. Its just odd that I get an error when this runs from the edit view, but not from the list view. -kaushik
on 2005-11-26 20:07
I don't think it is so strange. Action variables are made available if then view. If your edit action does not have @notes then neither will your view. Add "@notes = Note.find(:all)" to you edit action. Peter
on 2005-11-26 21:41
Oh you be good Peter! Yes, that worked. Thanks for your prompt replies. Adding <% @notes = Note.find(:all) %> worked. I'm still not sure why, though, since this code is not there in list.rhtml and list still works :( -kaushik
on 2005-11-26 21:49
You have controllers and views. Your views shouldn't contain code such as <% @notes = Note.find(:all) %> This code isn't in the list.rhtml, but it is in the app/controllers/yourcontroller.rb. Open that controller and look at def list @notes = Note.find(:all) end This code is executed before the view, so the @notes is in the list.rhtml view. But in the def edit .. end There isn't @notes = Note.find(:all). So if you alter it like this: def edit .. @notes = Note.find(:all) end It will work. You could also do it like this: def edit ... list end So you call the list action which sets the @notes variable in the edit action.
on 2005-11-26 22:24
On 11/26/05, Kaushik G. <email@example.com> wrote: > > Oh you be good Peter! > > Yes, that worked. Thanks for your prompt replies. Adding > > <% @notes = Note.find(:all) %> I think the view is not the best place to put this. You want this in your edit action (not view). Even if you do want it in your view try this in your controller file. def edit # your usual edit action code # add this line @notes = Note.find(:all) end I'm still not sure why, though, since this code is not there in > list.rhtml and list still works :( because "@notes = Note.find(:all)" is in the list action (not view). Look for it. Find it. Scaffold put it there didn't it? It doesn't matter if you write the code or scaffold writes the code for you. In either case @notes has to be filled. Rails doesn't fill it for you magically. Somewhere your code does. When you had the nil error it was because Rails had never seen @notes before and yet you still try to iterate over it. You have to tell Rails to fill @notes in the edit action if you want to use @notes in the edit view. Instance variable in an action are available in the associated view. I hope this makes more sense. Peter
on 2005-11-27 00:12
Hey Jules and Peter, Thanks for your explanations. RoR is making a bit more sense now. I never thought to look in the controllers code. Is there a manual or something that would take me through RoR systematically? The stuff I've found so far uses exmples, but as I'm finding out, I'm not understanding the structure of RoR very well. My skill levels are that I'm fairly experienced in C,C++ and in html and a bit of css. thanks -kaushik
on 2005-11-27 00:45
kghose wrote: > My skill levels are that I'm fairly experienced in C,C++ and in html and > a bit of css. > Check out www.softiesonrails.com, it's for those of us Microsofties trying to get our heads around concepts in rails.