Rails 3 Association NoMethodError

Question

I am relatively new to Rails and am a little bit in the Deep end. I am working in Rails 3 with a pre-existing MSSQL DB and having to retrofit out the models to fit.

I seem to have created my models without too many issues but have hit an issue with associations.

Here's my Schema for the two tables in question

  create_table "ip_addresses", :id => false, :force => true do |t|
    t.integer  "id",                        :null => false
    t.integer  "computer_id",               :null => false
    t.string   "ip",  :limit => 64, :null => false
    t.string   "ip_subnet",   :limit => 64, :null => false
    t.datetime "timestamp",                 :null => false
    t.datetime "created_at"
    t.datetime "updated_at"
  end



 create_table "computers", :id => false, :force => true do |t|
    t.integer  "id",                                                                    :null => false
    t.string   "uid",                      :limit => 128
    t.string   "enclosure_uid",            :limit => 128
    t.string   "name",                     :limit => 128
    t.integer  "status_id",                                                             :null => false
    t.integer  "designation_id",                                                        :null => false
    t.integer  "hardware_type_id",                                                      :null => false
    t.string   "hardware_model",           :limit => 128
    t.string   "processor_model",          :limit => 128
    t.integer  "processor_speed"
    t.integer  "processor_cores_per_proc", :limit => 1
    t.integer  "processor_count"
    t.decimal  "memory",                                  :precision => 9, :scale => 2
    t.decimal  "physical_disk",                           :precision => 9, :scale => 2
    t.integer  "san_disk"
    t.string   "os_name",                  :limit => 128
    t.string   "os_version",               :limit => 128
    t.string   "os_patchlevel",            :limit => 128
    t.integer  "campus_id",                                                             :null => false
    t.text     "description"
    t.datetime "modification_date",                                                     :null => false
    t.datetime "os_installdate"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

Here are the two models

class Computer < ActiveRecord::Base
  has_many :ip_addresses
end


class IpAddress < ActiveRecord::Base
  belongs_to :computer
end

It seems like the Association is working when I use the IpAddress Class, but not from the Computer class.

see below.

>> IpAddress.first.computer.name
"GC-PRD-PS02"
>> Computer.first.ip_addresses.ip
NoMethodError: undefined method `ip' for #<Class:0x10291cb18>
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.10/lib/active_record/base.rb:1014:in `method_missing'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.10/lib/active_record/associations/association_collection.rb:444:in `send'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.10/lib/active_record/associations/association_collection.rb:444:in `method_missing'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.10/lib/active_record/base.rb:1127:in `with_scope'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.10/lib/active_record/associations/association_proxy.rb:207:in `send'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.10/lib/active_record/associations/association_proxy.rb:207:in `with_scope'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.10/lib/active_record/associations/association_collection.rb:440:in `method_missing'
    from (irb):40

What is strange is that I can see the entire row object of the IpAddress Class by using

>> Computer.first.ip_addresses
[#<IpAddress id: 175, computer_id: 687, ip: "10.0.246.80", ip_subnet: "255.255.255.192", timestamp: "2011-08-03 11:17:57", created_at: "2011-10-07 01:06:16", updated_at: "2011-10-07 01:06:16">, #<IpAddress id: 176, computer_id: 687, ip: "192.168.234.235", ip_subnet: "255.255.255.255", timestamp: "2011-08-03 11:17:57", created_at: "2011-10-07 01:06:16", updated_at: "2011-10-07 01:06:16">, #<IpAddress id: 177, computer_id: 687, ip: "192.168.159.1", ip_subnet: "255.255.255.0", timestamp: "2011-08-03 11:17:57", created_at: "2011-10-07 01:06:16", updated_at: "2011-10-07 01:06:16">, #<IpAddress id: 178, computer_id: 687, ip: "192.168.42.1", ip_subnet: "255.255.255.0", timestamp: "2011-08-03 11:17:57", created_at: "2011-10-07 01:06:16", updated_at: "2011-10-07 01:06:16">]

I have search quite a bit to try and work this one out. I'm sure it's just my way of doing associations. Any help would be much Appreciated.

Thanks, Rob

Answer 1

As Computer.first.ip_addresses is an array, you need to do :

Computer.first.ip_addresses.first.ip

if you want the fist ip

Computer.first.ip_addresses.map(&:ip)

if you want all ips

Answer 2

Calling ip on a collection - that looks like the problem. Computer.first.ip_addresses[0].ip should work (presuming ip_addresses contains at least one element).

Also for learning, note what puts Computer.first.ip_addresses.class gives you.