Rails - Jan 2006 - Basic Many-to-One association

Sari,

I got the list display working without doing an explicit find.

It took a bit of a conceptual convulution to get it to work.  I was
thinking of it has Many Cases have One status.

There is no support for Many-to-One so I was a bit stumped.

Then I realized you just have to turn around your thinking to say One
Status has Many Cases.  Thus it is a One-to-Many relationship.  That
is descriped on page 234 of the book.

Below is a list of what I did in my code.

========1) I changed the name of the field "status_id" in the cases
table to
"case_status_id"

Then fixed the error this caused in case_controller.rb by simply
changing the name of the status_id field reference.

I did the same name change in app/view/case/list.rhtml, but then I
modified that line later anyway.

I''m sure I missed a bunch I was just trying to get a proof of concept
working.

2) I added a "belongs_to :case_status" line to the app/models/case.rb
file.

Thus rails now thinks that status is the master table and case is a
detail table.  Sort of strange but I think that is actually correct.

(ie. Each Status (One) has multiple Cases (Many) as detail records!!!)

We probably should add "has_many :cases" to the case_status model as
well.  I did not need that for the below to work, but it is part of
what is describe on page 234.

3) I edited the app/view/case/list.rhtml file to replace

     <%=h CaseStatus.find(a_case.status_id).status %>
with
     <%=h a_case.case_status.status %>	

Now that this is done, you should be able to use
"a_case.case_status.active" as well in the controller.

Hope that helps
Greg
--
Greg Freemyer
The Norcross Group
Forensics for the 21st Century

Apologies, I did not mean to send the below to the list.

Please ignore my previous post.

I was composing a question when I realized the answer.  I forgot to
take the list out of the to line.

Greg

On 1/26/06, Greg Freemyer <greg.freemyer@gmail.com>
wrote:
> Sari,
>
> I got the list display working without doing an explicit find.
>
> It took a bit of a conceptual convulution to get it to work.  I was
> thinking of it has Many Cases have One status.
>
> There is no support for Many-to-One so I was a bit stumped.
>
> Then I realized you just have to turn around your thinking to say One
> Status has Many Cases.  Thus it is a One-to-Many relationship.  That
> is descriped on page 234 of the book.
>
> Below is a list of what I did in my code.
>
> ========> 1) I changed the name of the field "status_id" in
the cases table to
> "case_status_id"
>
> Then fixed the error this caused in case_controller.rb by simply
> changing the name of the status_id field reference.
>
> I did the same name change in app/view/case/list.rhtml, but then I
> modified that line later anyway.
>
> I''m sure I missed a bunch I was just trying to get a proof of
concept working.
>
> 2) I added a "belongs_to :case_status" line to the
app/models/case.rb file.
>
> Thus rails now thinks that status is the master table and case is a
> detail table.  Sort of strange but I think that is actually correct.
>
> (ie. Each Status (One) has multiple Cases (Many) as detail records!!!)
>
> We probably should add "has_many :cases" to the case_status model
as
> well.  I did not need that for the below to work, but it is part of
> what is describe on page 234.
>
> 3) I edited the app/view/case/list.rhtml file to replace
>
>      <%=h CaseStatus.find(a_case.status_id).status %>
> with
>      <%=h a_case.case_status.status %>
>
> Now that this is done, you should be able to use
> "a_case.case_status.active" as well in the controller.
>
> Hope that helps
> Greg
> --
> Greg Freemyer
> The Norcross Group
> Forensics for the 21st Century
>

--
Greg Freemyer
The Norcross Group
Forensics for the 21st Century