Migration looks ok but is failing with an error - fluent

Question

I have Migrations creating my models in a MySQL DB and this is working.
Now, I want to seed the DB with some demo data, so I created a SeedDB Migration for the sole purpose of this (of course, this migration is running after creating all model migrations).
struct SeedDB: Migration {
func prepare(on database: Database) -> EventLoopFuture<Void> {
Setup.createDemoData(database: database)
...
}
}
I created a Setup model for doing setup stuff. At this moment, it is only creating the demo data, but may be used in the future for other things.
final class Setup {
static func createDemoData (database : Database){
let _ = Address.createDemoData (database: database).map{ address in
let _ = Site.createDemoData(address: address, database: database).map {site in
let _ = Appointment.createDemoData (site: site, database: database)
let _ = Company.createDemoData(site: site, database: database)
let _ = ....
}
}
As you can see, I have to nest some calls because a Site can not be made without having an Address. An Appointment, Company and others need to have a Site as parameter... (in those models that is defined using #Parent relations).
On the level on creating a Site from an address this works (as expected) perfect. However, if I want to create an Appointment (or Company) there is problem, even though the migration seems to be successful there is an error :
Would you like to continue? y/n> y Migration successful Fatal error:
Unexpectedly found nil while unwrapping an Optional value: file
NIO/CircularBuffer.swift, line 538
My models look like:
In each of my Models I have one of the following versions of these functions (depending on the needs) :
static func createDemoData (database: Database) -> EventLoopFuture<myModel> {
let newMyModel = myModel(param1: "some stuff", param2: "demo info")
return newMyModel.save(on: database).map{newMyModel}
}
or
static func createDemoData (site: Site database: Database) -> EventLoopFuture<myModel> {
let newMyModel = myModel(param1: "some stuff", param2: "demo info")
return newMyModel.save(on: database).map{newMyModel}
}
or similar...
FYI removing the .save(on: database) in the createDemoData in Appointment or Company makes the error not happening (but also not saving the instance to the DB)
Added model Appointment per request of 0xTim
static func createDemoData (site: Site, database: Database) -> [Appointment]{
var appointment: Appointment
var appointments : [Appointment] = []
let today = Date()
let day = TimeInterval(24.0 * 3600.0)
//Planned appointments
appointment = Appointment(siteID: site.id!, appointmentDate: (today+(3*day)), description: "Call James Bond")
let _ = appointment.save(on: database)
appointments.append(appointment)
....
As far as I know site.id! is not the culprit, since it is created in the Setup Model with the createDemoData for the appointment in its closure. (see code above).
Added createDemoData for Site class per request of 0xTim
static func createDemoData (address : Address, database: Database) -> EventLoopFuture<Site> {
let site = Site(name: "mySite", addressID: address.id!)
return site.save(on: database).map{site}
}
Again, address.id! should not be the problem as Site.createDemoData is in the closure of the address creating (so it should exist).

Answer 1

The issue you have is that you're not handling your futures. Every time you do
let _ = appointment.save(on: database)
Or similar you're telling the compiler to return immediately whether or not the save has returned or even succeeded. You need to handle the futures correctly with map/flatMap. It's the same with your migration
let _ = Address.createDemoData (database: database).map{ address in
let _ = Site.createDemoData(address: address, database: database).map {site in
let _ = Appointment.createDemoData (site: site, database: database)
let _ = Company.createDemoData(site: site, database: database)
let _ = ....
}
}
There's no guarantee (and it's quite likely) that you'll attempt to create the Appointment before the Address has completed etc