We're creating a flight scheduling program that schedules employees and planes for flights.

Here are the models that currently exist
Airport
Pilot
FlightAttendant
Aircraft

We are starting with only four airports. We want to fill in the four airports in the Airports table as soon as the app launches, and then make a self-join table from the Airports that lists all possible origin-destination combinations and their duration.

How would we do that?

I've seen some stuff online about it but it looks like its done when we create the models, but our models are already made, so I can't figure out the migration and how to fill in that table automatically. We know the durations and just need to feed them in.

EDIT:

In response to the flight times: we plan to store them as an integer which is the number of minutes it takes to complete a flight. The airports are in Midwestern cities chosen at random in the Central Time Zone.

Lincoln and Iowa City: 32 mins

Lincoln and Evanston: 57 mins

Lincoln and West Lafayette: 62 mins

Iowa City and Evanston: 24 mins

Iowa City and West Lafayette: 31 mins

Evanston and West Lafayette: 13 mins

For further detail

This is the specific migration which created the Airports table

class CreateAirports < ActiveRecord::Migration[5.2]
 def change
 create_table :airports do |t|
 t.string :full_name
 t.string :flight_code

 t.timestamps
 end
 end
end

full_name is simply the name like Evanston. flight_code is the the three letter code to represent it, like EVA.
The model is currently empty. Do I need to add something in it first before I add the association columns, or do I need to generate the migration to create the join table and then alter the Airport model?

You can run ruby code after the migration, Rails code in this case:

class CreateAirports < ActiveRecord::Migration[5.2]
 def change
 create_table :airports do |t|
 t.string :full_name
 t.string :flight_code

 t.timestamps
 end

 Airport.create(params_for_airport1)
 Airport.create(params_for_airport2)
 Airport.create(params_for_airport3)
 Airport.create(params_for_airport4)
 end
end

Then, for the durations table, I imagine you'll have something like a "FlightDuration" using a table with 3 columns: airport_from_id, airport_to_id, duration. You can do the same as before, you create the table and right after the create_table just create the objects with the data.

You'll have to add the relationships to Airport and to FlightDuration, something like:

class Airport < ApplicationRecord
 has_many :flight_durations_from, class_name: 'FlightDuration', inverse_of: :airport_from
 has_many :flight_durations_to, class_name: 'FlightDuration', inverse_of: :airport_to
end

class FlightDuration < ApplicationRecord
 belongs_to :airport_from, class_name: 'Airport', foreign_key: :airport_from_id
 belongs_to :airport_to, class_name: 'Airport', foreign_key: :airport_to_id
end