rails-3.1 | Is this a case for a nested form or a case for something else?

Question

I am working on an app to be used as a logbook for aircraft. I may be headed in the wrong direction with design of my db. Any recommendations on that would be useful. Is this a situation for nested forms? Or is that only if I need to actually create a record for both models at the same time?

As of now this is how I have laid out the models:

class Location < ActiveRecord::Base
  has_many :aircrafts, :pilots
end

class Aircraft < ActiveRecord::Base
  belongs_to :location 
  has_many :trips
end

class Pilot < ActiveRecord::Base
  belongs_to :location 
  has_many :trips
end

class Trip < ActiveRecord::Base
  belongs_to :aircraft, :pilot
end

ActiveRecord::Schema.define(:version => 20120209014016) do

  create_table "aircrafts", :force => true do |t|
    t.string   "tail_number"
    t.decimal  "hobbs"
    t.integer  "location_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  add_index "aircrafts", ["location_id"], :name => "index_aircrafts_on_location_id"

  create_table "locations", :force => true do |t|
    t.string   "city"
    t.string   "state"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "pilots", :force => true do |t|
    t.string   "first_name"
    t.string   "last_name"
    t.string   "email"
    t.integer  "location_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  add_index "pilots", ["location_id"], :name => "index_pilots_on_location_id"

  create_table "trips", :force => true do |t|
    t.date     "date"
    t.integer  "aircraft_id"
    t.decimal  "hobbs_out"
    t.decimal  "hobbs_in"
    t.integer  "cycles_airframe"
    t.integer  "cycles_left"
    t.integer  "cycles_right"
    t.time     "time_out"
    t.time     "time_in"
    t.integer  "pic_id"
    t.integer  "sic_id"
    t.string   "flight_sequence"
    t.text     "remarks"
    t.integer  "miles"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

end

What I want to be able to do is to create a new trip record and update the :hobbs column in the Aircraft record. With the Aircraft table I essentially want to track the current hobbs time (or think of it as the current mileage on a car). When I create a new trip it will use the current hobbs time for the hobbs_out attribute and the hobbs_in will be recorded in the trip and be used to update the Aircraft.hobbs.

Can I do this with code in the trip_controller? Something like:

def create
  @trip = Trip.new(params[:trip])
  @aircraft = Aircraft.where(params[:trip][:aircraft_id])
  @aircraft.hobbs = params[:trip][:hobbs_in]
  @aircraft.save

  respond_to do |format|
    if @trip.save
      format.html { redirect_to @trip, notice: 'Trip was successfully created.' }
      format.json { render json: @trip, status: :created, location: @trip }
    else
      format.html { render action: "new" }
      format.json { render json: @trip.errors, status: :unprocessable_entity }
    end
  end
end

If it is more of a nested form circumstance, how would I get the form to just update the Aircraft record and create a new Trip record?

Thanks!

Answer 1

Personally I would actually have Planes and Airports and structure the db as follows via these rails associations and then go from there:

class Airport < ActiveRecord::Base
  has_many :planes
  belongs_to :trip
end

class Plane < ActiveRecord::Base
  belongs_to :Airport # Current location 
  has_many :trips
  has_many :pilots, :through => :trips
end

class Pilot < ActiveRecord::Base
  has_many :trips
  has_many :planes, :through => :trips
end

class Trip < ActiveRecord::Base
  belongs_to :plane
  belongs_to :pilot
  has_many :airports
end

I think the nesting you reference will be more relevant in designing your routes perhaps.
For instance if you are doing RESTful routes and you nest one :resource within another :resource than you get all the rails helpers to use that relationship. You just need to do a couple of things like have forms do form_for[OuterModelName, InnerModelName] . For the most part however Rails will handle the details.

For resources (think tables/models) that you do want to be able to access separately (think, you want to update a plane, independently of say an Airport) then you need to have resources :plane as a separate route line as(as well as having it nested), ie there will be two references to that resource.

As a final note, it's resources when you'll have an index view (multiple records) and resource when you are just using one instance ( show , edit , update , etc).