如何在swift 3中从核心数据中删除对象

Question

这就是我将数据保存到核心的方法，现在我想从整个数据中删除特定的对象。我该怎么做呢？

下面是我保存数据的方式：

func saveProductDetails(product : Product) {
        // set user_id 
        product.user_id = UserDefaults.sharedInstace.getCustomerId()
        //save data locally for the time been
        let entity = NSEntityDescription.entityForName("Product", inManagedObjectContext: self.writeContext)
        let category = NSEntityDescription.entityForName("Category", inManagedObjectContext: self.writeContext)
        let brand = NSEntityDescription.entityForName("Brand", inManagedObjectContext: self.writeContext)

        var entityProduct = NSManagedObject(entity: entity!, insertIntoManagedObjectContext:self.writeContext)
        var entityCategory = NSManagedObject(entity: category!, insertIntoManagedObjectContext:self.writeContext)
        var entityBrand = NSManagedObject(entity: brand!,insertIntoManagedObjectContext: self.writeContext)

        entityProduct = product.settingManagedObject(entityProduct)
        entityProduct.setValue(String(Utill.sharedInstace.getTimeStamp()), forKey: "time_stamp")
        entityProduct.setValue(Constant.Status.STATUS_NOT_VERIFIED, forKey: "status")


        if product.categoryObject != nil{
            product.categoryObject.user_id = UserDefaults.sharedInstace.getCustomerId();
            entityCategory = product.categoryObject.settingManagedObject(entityCategory)
        }

        if product.brandObject != nil{
            product.brandObject.user_id = UserDefaults.sharedInstace.getCustomerId();
          entityBrand = product.brandObject.settingManagedObject(entityBrand)
        }

        entityProduct.setValue(entityCategory, forKey:"category")
        entityProduct.setValue(entityBrand, forKey: "brand")

        writeContext.performBlock {
            do {

                try self.writeContext.save()

                self.managedContext.performBlock({
                    do{
                        try self.managedContext.save()
                    } catch let error as NSError  {
                        print("Could not save \(error), \(error.userInfo)")
                    }

                })
            } catch let error as NSError  {
                print("Could not save \(error), \(error.userInfo)")
                return
            }

        }

    }

这个Product对象与另外两个对象有关系，我只想删除特定的对象，而不是全部。这意味着在UITableView中删除( product.purchase_id == "selected_purchse_id")。

如何做到这一点？

Answer 1

检查此代码以执行swift 3核心数据操作

import CoreData

class CoreDataOperations: NSObject {

    // MARK: Save data
    func saveData() -> Void {
        let managedObjectContext = getContext()
        let personData = NSEntityDescription.insertNewObject(forEntityName: "Person", into: managedObjectContext) as! Person
        personData.name = "Raj"
        personData.city = "AnyXYZ"

        do {
            try managedObjectContext.save()
            print("saved!")
        } catch let error as NSError  {
            print("Could not save \(error), \(error.userInfo)")
        } catch {

        }

    }

    // MARK: Fetching Data
    func fetchData() -> Void {

        let moc = getContext()
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Person")

        do {
            let fetchedPerson = try moc.fetch(fetchRequest) as! [Person]

            print(fetchedPerson.count)
            for object in fetchedPerson {
                print(object.name!)
            }

        } catch {
            fatalError("Failed to fetch employees: \(error)")
        }

    }



    // MARK: Delete Data Records

    func deleteRecords() -> Void {
        let moc = getContext()
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Person")

         let result = try? moc.fetch(fetchRequest)
            let resultData = result as! [Person]

            for object in resultData {
                moc.delete(object)
            }

            do {
                try moc.save()
                print("saved!")
            } catch let error as NSError  {
                print("Could not save \(error), \(error.userInfo)")
            } catch {

            }





    }

    // MARK: Update Data
    func updateRecords() -> Void {
        let moc = getContext()

        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Person")

        let result = try? moc.fetch(fetchRequest)

            let resultData = result as! [Person]
            for object in resultData {
                object.name! = "\(object.name!) Joshi"
                print(object.name!)
            }
            do{
                try moc.save()
                print("saved")
            }catch let error as NSError {
                print("Could not save \(error), \(error.userInfo)")
            }


    }

    // MARK: Get Context

    func getContext () -> NSManagedObjectContext {
        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        return appDelegate.persistentContainer.viewContext
    }
}

您可以从https://github.com/rajkumar24u/CoreDataOperations获得更多信息