使用Swift更新实体记录而不是使用CoreData创建新记录

Question

I need to fetch some information from the server.
and then I need to save them using CoreData.
The problem is that the same record with same attributes is saved several times.
I want to save just new records to the CoreData and update the existing ones.

func saveChanges() throws {
        var error: ErrorType?
        mainQueueContext.performBlockAndWait () {
            if self.mainQueueContext.hasChanges {
                do {
                    try self.mainQueueContext.save()
                } catch let saveError {
                    error = saveError
                }
            }
        }
        if let error = error {
            throw error
        }
   }

func fetchRecentPosts(completion completion: (PostResult) -> Void){

   .
   .
   .
   do{
        try self.coreDataStack.saveChanges()
        print("now data is saved in this device")

   }
   catch let error {
        result = .Failure(error)
   }
   .
   .
   .
}

My idea is to check if that id was saved. If it was saved before I should not add another record. Then how can I update the existing one? And is it a good way to solve this problem?

Answer 1

First check if your record exists in DB

static func getMyRecord(with id : String, context : NSManagedObjectContext) -> MyRecord? {
            let fetchRequest: NSFetchRequest< MyRecord> = MyRecord.fetchRequest()
            fetchRequest.predicate = NSPredicate(format: "id = %@", id)
            let foundRecordsArray = try! context.fetch(fetchRequest)
            if foundRecordsArray.count > 0 {
                return foundRecordsArray[0]
            }
            return nil
        }

While inserting if available update it else create new record.

static func insertRecord(_ record : MyRecord, context : NSManagaedObjectContext) {
    let foundRecord = DataInserterClass. getMyRecord(with: yourID, context: context)
            if foundRecord == nil {
                //create new record
            }
            else {
                //update foundRecord
            }
            try! context.save()
}