Core-data insert multiple objects - swift

Question

i am struggling again to solve a core Data task which keeps failing randomly on me
The following code is building my initial database, which is necessary for the app to work properly
(...)
let context = await (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
(...)
for person in groupOfPeople { //singlePerson (codable Struct) <> SinglePerson (NSManagedObject)
saveSinglePerson(sPerson: person, context: context)
counter+=1
}
logComment = logComment + "..success!(\(counter))"
func saveSinglePerson(sPerson: singlePerson, context: NSManagedObjectContext) {
let newSinglePerson = SinglePerson(context: context)
newSinglePerson.id = sPerson.ID
newSinglePerson.name = sPerson.name
newSinglePerson.age = sPerson.age
(...)
context.performAndWait {
do {
try context.save()
}catch let error {
print(error)
Logging.insertError(message: "IMPORT ERROR: \(error.localizedDescription)", location: "buildDatabase20")
}
}
}
Now here's my problem:
At first i didn't even notice there is a problem, because everything is working fine and all objects get saved as they are supposed to be,
but indeed there is one, because: i am randomly getting an error like so:
error= Error Domain=NSCocoaErrorDomain Code=134030 "An error occurred while saving." UserInfo={NSAffectedObjectsErrorKey=(
"<AppName.SinglePerson: 0x60000104e7b0> (entity: SinglePerson; id: 0x600003337ce0 <x-coredata:///SinglePerson/t3081F988-C5D1-4532-AD81-46F3B4B10215139>; data: {\n id = 138;\n name = testname;\n age = \"25\";\n })"
and i get this error multiple times (20x-150x), with just this one single ID, in this example 138, but it is a different id each time...
i investigate this situation for days now, and i just can't wrap my head around this..
what i found out by now is:
the method should insert 150 rows, and if this error occurs it is not just a count of 149, it's like 87, or 127, or whatever
seems like an object gets stuck in the context, and every execution after the first error fails and is throwing the (same) error..
i tried to fetch those new written data directly after i inserted them, and i always get the same (wrong) count of 150..
i know that this count is not legit because if i take a look at the sqllite file, is see just 87, or 127 or whatever row count..
i do this fetch again with the same context, this is why i think that the issue is within my NSManaged context..
why is this happening on me? and why does this happen sometimes but not all the time?
How do i solve it?

Answer 1

i've found a solution to fix this issue, even though i now know that i will have rework all Core Data interactions from the ground up, to make it real stable and reliable..
this is my first swift project, so along the way things got pretty messy tbh :)
fix: the fact that i save all created objects at once now instead of saving each item on its own, did work and solved the issue for me at this very moment :)
maybe this is helpful for somebody else too ;)
(...)
let context = await (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
(...)
var personArray = [SinglePerson]()
for person in groupOfPeople {
let newSinglePerson = SinglePerson(context: context)
newSinglePerson.id = sPerson.ID
newSinglePerson.name = sPerson.name
newSinglePerson.age = sPerson.age
(...)
personArray.append(newSinglePerson)
}
context.performAndWait {
do {
try context.save()
} catch let error {
print(error.localizedDescription)
}
}