Question

Hey all, I have been away from rails for a while and have been catching up to rails 3, I think my problem might stem from me using an unsupported syntax from rails 2 that didnt make it to rails 3. Anyways, my problem might be to broad but while I have been able to fix all the other problems with this app, this one still puzzles me.

On the home page of the site there is this code:

<%- unless @requested_contacts.empty? -%>
  <h2>Contact Requests</h2>
  <ul class="list requests small">
    <%- @requested_contacts.each do |contact| -%>
      <%- conn = Connection.conn(current_user, contact) -%>
      <li>

        <p><%= person_link contact %></p>
        <p class="meta published">
          <%= time_ago_in_words(conn.created_at) %> 
          ago
        </p>
        <p>
          <%= link_to "Respond", edit_connection_path(conn) %> |
          <%= link_to "View profile", contact %>
        </p>
      </li>
    <%- end -%>
  </ul>
<%- end -%>

When I click respond instead of getting to the Connection edit page, I get an error:

undefined method `contact' for nil:NilClass

app/controllers/connections_controller.rb:15:in `edit'

{"id"=>"4"}

The controller code is:

 def edit    
    @contact = @connection.contact
  end

The relavent models are, Person.rb:

  has_many :connections

  has_many :contacts, :through => :connections, :order => 'people.created_at DESC'
  has_many :requested_contacts, :through => :connections, :source => :contact

Connection.rb:

  belongs_to :person
  belongs_to :contact, :class_name => "Person", :foreign_key => "contact_id"

  def conn(person, contact)
    find_by_person_id_and_contact_id(person, contact)
  end

The edit page I am trying to get to is:

<h2>Contact request</h2>

<p>You have a contact request from <%= @contact.name %></p>

<% form_for(@connection) do |f| %>
  <p>
    <%= f.submit "Accept", :class => "button" %>
    <%= f.submit "Decline", :id => nil, :class => "button" %>
  </p>
<% end %>

I think that is all the relevant code to this issue. If there is anything else you might need to see please let me know, I am very grateful for any an all help. Sorry if it is glare lying obvious, I am learning ruby and rails as a hobby (and loving it so far!).

Answer 1

When you see this error:

undefined method `contact' for nil:NilClass

It usually means you’re trying to call a method on an unassigned variable. Since the error points to the controller, and the code you’ve shown us is:

def edit    
  @contact = @connection.contact
end

I’m going to guess that @connection is unassigned. Normally you would expect to have a finder method to retrieve the value before using it, like:

@connection = Connection.find(params[:id])

Sometimes this code is placed in a before_filter, to reduce duplication. If you do have such a filter, perhaps it is not being reached. It’s hard to know without seeing the rest of the controller code.