Core Data fetching data and looking for duplicate - ios

Question

I want to fetch data from Core data and look for duplicats and then only save the data then there is no duplicate of the movieid.
Maybe some one can help me ..
How can I compare the result with the movieid string ?
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "MovieData")
//request.predicate = NSPredicate(format: "movieid = %#", movieID)
request.returnsObjectsAsFaults = false
do {
let result = try context.fetch(request)
for data in result as! [NSManagedObject] {
print(data.value(forKey: "movieid") as! String)
}
} catch {
print("Failed")
}

Answer 1

Almost. Apply the predicate to get only the record with the specific movieID. However it assumes that movieID is an object (NSNumber), if it's an scalar Int you have to use %ld as placeholder.
If the fetch returns an empty array there is no duplicate and you can insert a new object
let request = NSFetchRequest<NSManagedObject>(entityName: "MovieData")
request.predicate = NSPredicate(format: "movieid = %#", movieID)
do {
let result = try context.fetch(request)
if result.isEmpty {
let newMovie = NSEntityDescription.insertNewObject(forEntityName: "MovieData", into: context) as! MovieData
newMovie.movieid = movieID
try context.save()
}
} catch {
print(error)
}

Answer 2

While saving in core data you need to create predicate and in there you need to check if there are values already saved with same "movieid" then it has to be updated , this way you won't have duplicate data . Please refer the method and try using the same for saving the values in DB . This way duplicate values won't be saved in DB
class func insertupdaterecord (movieID:String, context: NSManagedObjectContext)
{
let entityDescription = NSEntityDescription.entity(forEntityName: "movie", in: context)
let pred = NSPredicate(format: "movieid = %#", movieID)
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "movie")
fetchRequest.entity = entityDescription
fetchRequest.predicate = pred
let result = try! (context.fetch(fetchRequest) as NSArray).lastObject
let updateInsertInfo : movie
if result != nil
{
updateInsertInfo = result as! movie
}
else
{
print("Record not found!")
}
do
{
try context.save()
}
catch let error as NSError
{
print("Error while saving \(error) in database.")
}
}

Answer 3

Create a cache for movieid values to check for duplicates and loop through the fetched result and delete any objects with a movieid already in the cache and then save once the loop is done.
var selection: [String] = []
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "MovieData")
request.returnsObjectsAsFaults = false
do {
let result = try context.fetch(request)
for data in result as! [NSManagedObject] {
guard let movieId = data.value(forKey: "movieid") as? String else {
context.delete(data) // or however you want to handle this situation
continue
}
if selection.contains(movieId) {
context.delete(data)
} else {
selection.append(movieId)
}
}
try context.save()
} catch {
print("Failed")
}