RLMException attempting to create object with an existing primary key after check

Question

I'm receiving an RLMException for the following reason:

Attempting to create an object of type 'Student' with an existing primary key value '258975085-504336622-62850'.

The confusing part is that it's occurring just after a check that there are no existing objects with this key in the Realm.

let realm = try Realm()
if let info = realm.object(ofType: Student.self, forPrimaryKey: newStudent.userId) {
    try realm.write {
        info.name = newStudent.name
        info.school = newStudent.school
        info.email = newStudent.email
    }
}
else {
    try realm.write {
        realm.add(newStudent) //RLMException occurs here
    }
}

This code is all running asynchronously on the GCD utility queue, inside a do/catch block. It's triggered by a button in the user interface, but nothing else is accessing realm at the same time.

Why could that if statement allow the else code to run?

Answer 1

In my case, I added condition to check whenever new user logs in:

if newStudent == nil{
     self.realm.add(newStudent, update: .all)
}

Answer 2

try! self.realm.write {
    self.realm.add(newStudent, update: true)
}

You're adding same Object (student) with existing primary key. So you can just update current one. Instead of deleting and adding new one.