how to get values of child object

Question

I've got some nested objects in rails. User -> has_many :tasks -> has_one :location.

Yesterday, I thought I was having trouble linking the location values to the task, but now I realize that I'm not able to get the values to output in show either.

I can get the output via debug

<%= for task in @user.tasks %>
        <%= debug task.locations %>
<% end %>

outputs

--- !ruby/object:Location
attributes:
    id: "1"
    address: "testing address"
    city: "chicago"
attributes_cache:  {}

changed_attributes: {}

etc. etc. etc.

So I thought if I used

<%= task.locations.address %>

Rails would give me the address field. but I get an

undefined method 'address' for nil:NilClass

any suggestions on what I've got wrong?

---------- update, including models ---------------- My models for tasks & locations are

class Task < ActiveRecord::Base
     attr_accessible :user_id, :date, :description, :location_id

     belongs_to :user
     has_one :location
end

class Location < ActiveRecord::Base
     attr_accessible :address, :city, :state, :zip

     has_many :tasks
end

christianblais christianblais · Accepted Answer · 2011-02-16T21:55:16

If task has_one location, you'll need to do task.location.address without the s at the end of location, as has_one returns the actual object and not a collection. You'll also need to be sure your location exists before calling it's address method or you'll get an error in case of a nil location. You could be interested in the try method, such as task.location.try(:address).

how to get values of child object

1 Answers