ruby - I have somehow broken my Rails app - the dreaded NoMethod Error -

the error message nomethoderror in circuit#update undefined method 'network_address' nil:nilclass , related line in view:

<td><%= logical_interface.subnet.network_address %></td> 

everything working earlier , i've managed break somehow when restarted local server.

update.rhtml

<table id="logical_interfaces">     <% @logical_interfaces.each |logical_interface| %>         <tr id="logical_interface_<%= logical_interface.id %>">             <td><%= logical_interface.description %></td>             <td><%= logical_interface.subnet.network_address %></td>             <td><%= logical_interface.bandwidth %></td>             </td>         </tr>     <% end %> </table> 

logical_interface.rb

belongs_to :subnet belongs_to :circuit 

subnet.rb

belongs_to :logical_interface belongs_to :circuit 

circuit.rb

has_many :subnets has_many :logical_interfaces 

circuit_controller.rb

the crud being done inside controller of model because main object else runs off.

def update    ....   if params[:id]     @circuit = circuit.find(params[:id])   end    @logical_interfaces = logicalinterface.find_all_by_circuit_id(@circuit.id)   ....  end 

as common bugs, i'll bet silly genuinely can't work out myself appreciate answers. have feeling it's relationships have been defined between models wrong.

subnet nil logical_interface. either add validation in logicalinterface model:

validates_presence_of :subnet 

or display network_address if subnet present.

<td><%= logical_interface.subnet.try(:network_address) %></td>