Realm Swift duplicates item with primary key -> Threading problem? - ios

Question

I'm using ReamSwift to store data in my iOS application and I have troubles to figure out, why sometimes objects are duplicated in my application.
I use an UUID as primary key on every object. This property is defined in a base class and all the others are subclasses of that.
I use the update approach with a dictionary. So new objects are created and existing should be updated.
I use a central class which holds the Realm object and handles the update. This method could be called from multiple different threads.
This is my base class
import RealmSwift
open class RealmObject : Object {
static let ID_ATTRIBUTE : String = "id"
#objc dynamic var id : String = ""
override public static func primaryKey() -> String? {
return "id"
}
}
Central class managing swift.
This class holds the Realm Object
public var realm: Realm {
var tempRealm: Realm?
do {
tempRealm = try Realm(configuration: configuration)
}
catch let err {
print("------ERROR----- initializing realm\n \(err)")
}
if let tempRealm = tempRealm{
return tempRealm
}
return self.realm
}
This is the update method in the class. As a fallback if the id property is not set, it will be set as it is the primary key
func update<T: RealmObject>(_ obj : T, values : [String:Any?] ) -> T? {
var vals = values
do {
var res : T?
try realm.write {
if let idattr = vals[T.ID_ATTRIBUTE] as? String {
if(idattr.isEmpty) {
vals[T.ID_ATTRIBUTE] = UUID().uuidString
}
} else {
vals[T.ID_ATTRIBUTE] = UUID().uuidString
}
res = realm.create(T.self, value: vals, update: .modified)
}
return res
} catch {
return nil
}
}
Could calling the update method cause in any case the duplication as I set the primary key of the object? The problem is, I cannot reproduce to find the problem, i just encounter the issue from time to time and in the field from users.
One interesting thing, when a copy is deleted, also the other object will be deleted.
This is the method which deletes objects by id and type
func delete<T: RealmObject>(_ id : String, _ type : T.Type) -> Bool {
do {
let obj = get(id, T.self)
if let obj = obj {
try realm.write {
realm.delete(obj)
}
return true
} else {
return false
}
} catch {
return false
}
}