Rails - Jul 2006 - how to get to the parent of a child object.

Hi, i have a problem with the following:

I have an application with patients <-->>consults
models are ok

in the view list_consults i do this:

for consult in @consults%>
    <tr>
    <td><%= consult.patient.name %></td>
    <td><%= consult.reason %></td>
    <td><%= consult.date %></td>
    <td><%= link_to ''Show'', :action =>
''show_consult'', :id => consult
%></td>
    </tr>
<% end %>

in my controler i have:

def list_consults
    @consults_pages, @consults = paginate :consults, :per_page => 8
end

i cant get to the lastname of the patient, the error i get

"undefined method `name'' for nil:NilClass

what am i doing wrong?

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I don''t know if this is the case or not, but if you are not requiring a
patient to be assigned elsewhere then some of the records will not have 
a patient record. When it loops and reaches one such consult, then the 
error will be thrown. You can fix it by giving the line a condition:

<%= consult.patient.name if consult.patient %>

Hope this helps...

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Me again. There has got to be a better way of doing what I just wrote 
there. With what I have there will be an additional query for each 
consult record to see if it has a patient. If you have this in a lot of 
rows and columns on a list page, then that''s a lot of queries. It does 
the job, but with a lot of extra querying.

I''m not sure of another way of doing that...

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robert bradford wrote:
> <%= consult.patient.name if consult.patient %>
> There has got to be a better way of doing what I just wrote 
> there. With what I have there will be an additional query for each 
> consult record to see if it has a patient.
I disliked that by-product as well and instead have been using:

<%= consult.patient.name if consult.patient_id %>

-- 
Posted via http://www.ruby-forum.com/.

robert bradford wrote:
> I don''t know if this is the case or not, but if you are not
requiring a
> patient to be assigned elsewhere then some of the records will not have 
> a patient record. When it loops and reaches one such consult, then the 
> error will be thrown. You can fix it by giving the line a condition:
> 
> <%= consult.patient.name if consult.patient %>
> 
> Hope this helps...

thanks a lot robert,
indeed there was a problem in my table, there were some records in it 
with no parent. now it works

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Lonnie Warpup wrote:
> robert bradford wrote:
>> <%= consult.patient.name if consult.patient %>
> 
>> There has got to be a better way of doing what I just wrote 
>> there. With what I have there will be an additional query for each 
>> consult record to see if it has a patient.
> 
> I disliked that by-product as well and instead have been using:
> 
> <%= consult.patient.name if consult.patient_id %>
Hi Lonnie-

I just tried changing one of my lists to do this, but I''m still showing
individual queries being done. In my application I have help desk 
tickets with the following belongs_tos:

department
user
category
assignee

On my list I want to show each of these. In my tickets controller I have 
the following:

@ticket_pages, @tickets = paginate :tickets, :per_page => 10, 
:conditions => conditions, :include => [:department, :category, :user, 
:assignee]

The :include option should (and does) create joins in the tickets query. 
I assume this would then cause those associations to not be loaded 
separately. In my view I have the following:

<% for ticket in @tickets %>
  <tr class="<%= cycle ''odd'',
''even'' %>">
    #...
    <td><%=h ticket.user.full_name if ticket.user_id %></td>
    <td><%=h ticket.department.name if ticket.department_id
%></td>
    <td><%=h ticket.category.name if ticket.ticket_category_id
%></td>
    <td><%=h ticket.assignee.full_name if ticket.assignee_id
%></td>
    #...
  </tr>
<% end %>

When load the page my terminal window shows individual queries being 
done still. Am I missing something?

Thanks,
Robert

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