A custom method for models

Rails 3.1.3

Say, I have models and associations like models:   Plan :flight_name_id: integer

  FlightName :departure_id :integer                         :destination_id :integer

  Place :city_id :integer

  City :name :string

Plan 1--n FlightName n--1 Place n--1 City

Apparently, a flight_name has connections to TWO places, where one of them refers to departure_id and another to destination_id. Corresponding place.id's are stored in them.

In a view, I would like to generate City.name's (string) for both departure place and destination place.

My question is: How can I achieve this?

in a view (html.erb template)

  plan.flight_name.plan

gives an error, "undefined method `place' for" obviously. I am guessing that a custom method needs to be defined in order to pull out City,name from a Plan.

Can anyone give me advice?

soichi

Rails 3.1.3

Say, I have models and associations like models:   Plan :flight_name_id: integer

  FlightName :departure_id :integer                         :destination_id :integer

  Place :city_id :integer

  City :name :string

Plan 1--n FlightName n--1 Place n--1 City

Apparently, a flight_name has connections to TWO places, where one of them refers to departure_id and another to destination_id. Corresponding place.id's are stored in them.

Show us the class definitions with has_many and belongs_to specifications. If the problem is that you do not know how to specify two places in the flight name then you need to do something like class Flightname   belongs_to :destination, :class_name => "Place", :foreign_key => "destination_id"   belongs_to :departure, :class_name => "Place", :foreign_key => "departure_id"

Then you can say flightname.destination and flightname.departure. You also have to put two equivalent has_many definitions in class Place. Have a look at the rails guide on activerecord associations and the rails docs for more details.

Colin

  belongs_to :destination, :class_name => "Place", :foreign_key => "destination_id"   belongs_to :departure, :class_name => "Place", :foreign_key => "departure_id"

I didn't know anything about ":foreign_key" option.

I put

class Place < ActiveRecord::Base   has_many :flight_names, :foreign_key => :departure_id   has_many :flight_names, :foreign_key => :destination_id end

class FlightName < ActiveRecord::Base   belongs_to :departure, :class_name => "Place", :foreign_key => :departure_id   belongs_to :destination, :class_name => "Place", :foreign_key => :destination_id ...

It works fine! Thanks Colin as always!

soichi

  belongs_to :destination, :class_name => "Place", :foreign_key => "destination_id"   belongs_to :departure, :class_name => "Place", :foreign_key => "departure_id"

I didn't know anything about ":foreign_key" option.

I put

class Place < ActiveRecord::Base   has_many :flight_names, :foreign_key => :departure_id   has_many :flight_names, :foreign_key => :destination_id

That won't work properly when you come to do place.flight_names, though the code you have so far may be ok. You did not look at the examples in the guide carefully enough. Check out section 2.10 and you will see that you need something like has_many :departure_flight_names, :class_name => "FlightName", :foreign_key => :departure_id has_many :destination_flight_names, :class_name => "FlightName", :foreign_key => :destination_id then you can say place.departure_flight_names and place.destination_flight_names

Though I am not sure about your choice of class name as FlightName. Should it not just be Flight or something similar?

Colin

That won't work properly when you come to do place.flight_names, though the code you have so far may be ok. You did not look at the examples in the guide carefully enough. Check out section 2.10 and you will see that you need something like has_many :departure_flight_names, :class_name => "FlightName", :foreign_key => :departure_id has_many :destination_flight_names, :class_name => "FlightName", :foreign_key => :destination_id then you can say place.departure_flight_names and place.destination_flight_names

Rails is amazingly fun to deal with...Now I have learned a lot. Thanks.

Though I am not sure about your choice of class name as FlightName. Should it not just be Flight or something similar?

FlightName only contains integer identification codes, and Flight includes Airline.company and Date as well, which are not apparent in this thread. So it's OK. Thanks, though.

soichi