Hello! I’m new to rails ad ActiveRecord, and have a very basic
problem.
I have a very basic rails app, which I want to contain computers, and
notes. Each computer has associated notes. I’m getting an error I’m
not fully understanding when I try to view a computer. The view
should include a listing of notes for the associated computer, but
instead, I get this:
Couldn’t find Note without an ID
The link that takes the user to the screen with the problem:
<%= link_to ‘Show’, :action => ‘show’, :id => computer %>
My controller:
def show
@computer = Computer.find(params[:id])
@notes = Note.find(params[:computer_id])
end
My view for show:
<% for column in Computer.content_columns %>
<%= column.human_name %>: <%=h @computer.send(column.name) %>
<% end %>
<% for note in @notes %>
<% for column in Note.content_columns %>
| <%=h note.send(column.name) %> |
<% end %>
<% end %>
<%= link_to ‘Edit’, :action => ‘edit’, :id => @computer %> |
<%= link_to ‘Back’, :action => ‘list_computers’ %>
I realize I’m not setting :computer_id anywhere, but using :id in my
controller for notes gives me the same issue, and I don’t want to pull
up notes with a particular id, but notes with a particular associated
computer. It seems like there should be a simple way to accomplish
this in rails, and I’m just missing it.
Thank you in advance!
On Jun 4, 2007, at 2:29 PM, Big Dave S. wrote:
My controller:
def show
@computer = Computer.find(params[:id])
@notes = Note.find(params[:computer_id])
end
Presuming you have models along the lines of:
class Computer < ActiveRecord::Base
has_many :notes
end
class Note < ActiveRecord::Base
belongs_to :computer
end
What you probably want for the above is:
def show
@computer = Computer.find(params[:id], :include => :notes)
@notes = @computer.notes
end
Or if you wanted to search the notes without actually loading the
Computer, and params[:id] included the computer id, you’d want:
def show
@notes = Note.find_by_computer_id(params[:id])
end
If you haven’t read Agile Web D. With Ruby on Rails or one
of the other rails books, it’d definitely be worth your while to do
so, to get a better understanding of how rails handles parameters,
and associations.
James.
Cheers,
Jodi
General Partner
The nNovation Group inc.
www.nnovation.ca/blog
On 4-Jun-07, at 2:29 PM, Big Dave S. wrote:
@notes = Note.find(params[:computer_id])
Hey Big Dave,
Note.find() is a finder that retrieves the row with the provided
primary key (so Note.find(1) will retrieve note with pk of 1).
To query all notes,
@notes = Note.find(:all, :conditions => [“computer_id = ?”, params
[:computer_id])
or better yet, since you’ve just retrieved the computer, then this
the way to go:
@notes = @computer.notes
sweet eh?
(as James suggested, pickup Pickaxe (er, ‘skateboard’). It’ll get you
over a bunch of early humps)
Jodi
On Jun 4, 2007, at 2:43 PM, Jodi S. wrote:
small correction -
@notes = Note.find_by_computer_id(params[:id])
will return one row. Note.find_all_by_computer_id will do a find(:all)
Yeah, sorry – trying to get a response sent out quickly before
getting back to work.
James.
On 4-Jun-07, at 2:38 PM, James S. wrote:
The link that takes the user to the screen with the problem:
class Computer < ActiveRecord::Base
@computer = Computer.find(params[:id], :include => :notes)
If you haven’t read Agile Web D. With Ruby on Rails or one
of the other rails books, it’d definitely be worth your while to do
so, to get a better understanding of how rails handles parameters,
and associations.
James.
small correction -
@notes = Note.find_by_computer_id(params[:id])
will return one row. Note.find_all_by_computer_id will do a find(:all
see my forthcoming announcement on find_by_associations to clean this
up even more
Jodi
Big Dave S. wrote:
The link that takes the user to the screen with the problem:
<%= link_to ‘Show’, :action => ‘show’, :id => computer %>
I think you mean :id => @computer in the above line
–
Cheers,