Related Models

rubyonrails-talk
1

I am still somewhat new to rails and I am not getting the results I am expecting with my models.. perhapse I do not understand something, or just didn't set something up right.

I have three models:

class Coordinator < ActiveRecord::Base   belongs_to :county   belongs_to :state end

class State < ActiveRecord::Base   has_many :counties   has_many :coordinators, :through => :counties   accepts_nested_attributes_for :counties, :coordinators end

class County < ActiveRecord::Base   belongs_to :state   has_one :coordinator   accepts_nested_attributes_for :coordinator   scope :returncounty, lambda {|state| where(:state_id => state)} end

When I try and do something like this in my view

<% @states.each do |state| %> <% state.counties.each do |county| %> <p><%= county.name %> <%= county.coordinator.name %></p> <% end %> <% end %>

I am getting:this error. I have tried several variations on this theme.. so I feel like I am stuck in my understanding of how rails associations work. Can someone point me in the right direction? undefined method `name' for "#<Coordinator: 0x00000003a83128>":Coordinator

2

That's a fairly straightforward, self-explanatory error, that's got nothing to do with associations. It's telling you that Coordinator has no method "name". Have you created and run a migration to add a field called "name" to that table? Can you check in your DB management tool to check the field is there. Can you open a console and execute "Coordinator.new" (or just "Coordinator") and see the list of available attributes/field names.

Let us know the result. Regards,

3

Probably not associated with your problem but there is something not right above, you have two routes to coordinator from state. You have coordinator belongs to state (implying coordinator has a state_id column) and so you should also have state has many coordinators (which you have not specified). You also have coordinator belongs to county and county has one coordinator, but then in state you also have state belongs_to county and state has_many coordinators through counties. So when you say @state.coordinators it will get the coordinators from the counties, in which case you should not have coordinator belongs to state.

Colin

4

Woops in all my changes I put name instead of firstname on my coordinators.. This is now correct but the original issue is still there.. which is when I try and call state.county.name or coordinator.state.name or county.state.name.

I am quite sure that county.name exists and that state.name exists.

I ran some commands in the console, here is what I get:

examplestate = State.find(1) => #<State id: 1, name: "Alabama", abreviation: "AL", created_at: "2011-04-04 16:32:08", updated_at: "2011-04-04 16:32:08">

examplestate.name => "Alabama"

examplecounties = examplestate.counties => [#<County id: 3, name: "Baldwin County", state_id: 1, created_at: "2011-04-04 16:32:32", updated_at: "2011-04-04 16:32:32">, #<County id: 4, name: "Cherokee County", state_id: 1, created_at: "2011-04-04 16:32:32", updated_at: "2011-04-04 16:32:32">, #<County id: 5, name: "Chilton County", state_id: 1, created_at: "2011-04-04 16:32:33", updated_at: "2011-04-04 16:32:33">, #<County id: 6, name: "Clarke County", state_id: 1, created_at: "2011-04-04 16:32:33", updated_at: "2011-04-04 16:32:33">, #<County id: 7, name: "Colbert County", state_id: 1, created_at: "2011-04-04 16:32:33", updated_at: "2011-04-04 16:32:33">, #<County id: 8, name: "Crenshaw County", state_id: 1, created_at: "2011-04-04 16:32:33", updated_at: "2011-04-04 16:32:33">, #<County id: 9, name: "Cullman County", state_id: 1, created_at: "2011-04-04 16:32:33", updated_at: "2011-04-04 16:32:33">, #<County id: 10, name: "DeKalb County", state_id: 1, created_at: "2011-04-04 16:32:33", updated_at: "2011-04-04 16:32:33">,etc.. etc..

examplecounties.each do |county|    puts county.coordinator.firstname end

Jessica Ron P. Dale Gerry Garry Tami Samuel etc. etc.

So when I call a coordinators firstname from a county, from a state.. it seems to work.. but then when I try that in the view for instance:

My state controller calls @state.all

and in the state index view I have:

<% @states.each do |state| %> <strong><%= state.name %></strong> <% state.counties.each do |county| %> <p><%= county.coordinator.firstname %> </p> <% end %> <% end %>

I get this error: undefined method `firstname' for nil:NilClass

5

As another example I can also put in the same view:

<% @states.each do |state| %>   <% state.coordinators.each do |coordinator| %>   <p><%= coordinator.county.name %> </p>   <% end %> <% end %>

and I get undefined method `name' for nil:NilClass

6

That's a *different* error to what you had before. That's telling you that the thing you're trying to call ".firstname" on is nil. ie: there is no coordinator for the given county.

You can guard against this error any number of ways, an easy one being:   <%= county.coordinator.firstname if county.coordinator %>

7

Great.. I knew it had to be something so simple.. You helped me get past the brick wall!

I had not even considered that nearly 70% of my counties have no coordinator!!!! DOH!

thanks for your help