Swift: CoreData call to specific object ID - ios

Question

I'm discovering new concepts as a fresh developer, I have been trying to understand core data, and run into an issue with a tutorial I've been walking through. I am getting an error when I call an item using the Object ID. The error is - Type 'Person.Type' has no subscript members. it may be because I am just not doing it correctly, or some other reason. I'm sure someone can shine some light on the subject
Here is a function I wrote to get a specific item out of the Data Stack,
func getObjectById(id: NSManagedObjectID) -> Person?{
return context.objectWithID(id) as? Person
}
Here is how I am calling the function
func callFirstObject(){
let context = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
let personService = PersonService(context: context)
let firstPerson = personService.getObjectById(Person[0].objectID!)
}
and from there I am just calling callFirstObject() inside a button.
Edit: I have a function to call all of my objects
func getAllObjects() -> [Person]{
return getObject(withPredicate: NSPredicate(value: true))
}
and a function to call all of my objects with a predicate
func getObject(withPredicate queryPredicate: NSPredicate) -> [Person]{
let fetchRequest = NSFetchRequest(entityName: Person.entityName)
fetchRequest.predicate = queryPredicate
do {
let response = try context.executeFetchRequest(fetchRequest)
print("\(response)")
return response as! [Person]
} catch let error as NSError {
// In case of failure
print("There was an error - \(error)")
return [Person]()
}
}
I am just trying to call a specific name in the stack.
If more information is needed, I am glad to provide.

Answer 1

Person has no subscript members because Person is the class name. The subscript, [0], should be called on an array of Person objects.
That could look something like this:
func callFirstObject(){
let context = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
let personService = PersonService(context: context)
// Person Array
let persons: [Person] = [person1, person2, person3 ]
let firstPerson = personService.getObjectById(persons[0].objectID!)
}
Edit: I'm kind of confused the logic though. If you have the person already, you have to in order to access the objectID, then I don't see why you need to fetch it again. Can we see some more context around these two methods?
Answering your question from the comment below:
If you want to get all of the records for the Person model you can do as follows:
let appDelegate =
UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "Person")
do {
let results =
try managedContext.executeFetchRequest(fetchRequest)
people = results as! [NSManagedObject]
} catch let error as NSError {
print("Could not fetch \(error)")
}
This will give you all of the Person objects stored in Core Data