Core Data Insert one to many with multiples relationships - swift

Question

Good afternoon!
I am using the core date to save the following entity.
Training Program > Activities > Series
When saving the activities within the program, I am using the method.
let programTranningDB = NSEntityDescription.insertNewObject(forEntityName: "ProgramTranningDB", into: self.getContext())
(programTranningDB as! ProgramTranningDB).addToActivities(activities)
do{
try self.getContext().save()
} catch {
print(error)
}
How can I add series into activities?
Can someone help me?

Answer 1

Assuming your model looks a little like this:
A TrainingProgram can have many activities.
An Activity can have many series.
You will add an instance of Series to an Activity in the same way as you add the Activity to a TrainingProgram.
You can use the auto-generated method on Activity of addToSeries(_:)
I usually keep all my data domain logic contained in a class to aid testing and separation of concerns.
class DomainLogic {
var context: NSManagedObjectContext
init(context: NSManagedObjectContext) {
self.context = context
}
func addNewProgram(named: String) -> TrainingProgram {
guard let program = NSEntityDescription.insertNewObject(forEntityName: "TrainingProgram", into: context) as? TrainingProgram else {
preconditionFailure("TrainingProgram should be created here")
}
program.name = named
return program
}
func addNewActivityToProgram(_ program: TrainingProgram) -> Activity {
guard let activity = NSEntityDescription.insertNewObject(forEntityName: "Activity", into: context) as? Activity else {
preconditionFailure("Activity should be created here")
}
program.addToActivities(activity)
return activity
}
func addNewSeriesToActivity(activity: Activity) -> Series {
guard let series = NSEntityDescription.insertNewObject(forEntityName: "Series", into: context) as? Series else {
preconditionFailure("Series should be created here")
}
activity.addToSeries(series)
return series
}
}
Which leads to a simple sequence to create a new Series and add it down the chain.
var context: NSManagedObjectContext!
func createSeries() -> Series {
let logic = DomainLogic(context: context)
let program = logic.addNewProgram(named: "Fatima's Program")
let activity = logic.addNewActivityToProgram(program)
let series = logic.addNewSeriesToActivity(activity: activity)
return series
}
You'll also need logic to recover existing TrainingProgram objects from the database.