CoreData 实现 swift 3

Question

我在项目中实施核心数据时遇到问题。它似乎能够保存但不能获取。这是代码

let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    let entity = NSEntityDescription.entity(forEntityName: "Utente", in: context)
    let item = NSManagedObject(entity: entity!, insertInto: context)
    var utente: Profilo? = nil
    let vc = CustomTabBarController() as UIViewController
    let vc1 = LoginController() as UIViewController
    // Configure Fetch Request

    do {
        let request: NSFetchRequest<NSFetchRequestResult> = Profilo.fetchRequest()
        let result = try context.fetch(request) as Profilo
        utente = result as Profilo
        print()
        if utente?.type != nil {
            if utente?.type == "students"{
                print("students")
                    present(vc, animated: true, completion: nil)
            }
            if utente?.type == "parents"{
                print("parents")
                present(vc, animated: true, completion: nil)

            }
            if utente?.type == "teachers"{
                print("teachers")
                present(vc, animated: true, completion: nil)

            }
        } else {
            print("variable type empty")
            present(vc1, animated: true, completion: nil)

        }
    } catch {
        let fetchError = error as NSError
        print(fetchError)
    }

我也在结果行中得到错误：无法使用 (NSFetchRequest)

类型的参数列表调用 'fetch'

Answer 1

语法应该是

let request: NSFetchRequest<Profilo> = Profilo.fetchRequest()
let result = try context.fetch(request) as! [Profilo] // returns always an array.

请考虑默认初始化器 CustomTabBarController() 和 LoginController() 将不起作用。

Answer 2

正如我们所同意的，我将发布我的核心数据功能，它们可能不是最好的方式，但它们在我的项目中有效。我的实体称为目标。

// MARK: - Core data funcitons

func loadCoreData(){
    goalsArray.removeAll()

    //let request = NSFetchRequest<Goals>(entityName:"Goals")
    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

do{
let fetchRequest : NSFetchRequest<Goals> = Goals.fetchRequest() as! NSFetchRequest<Goals>
let sortDescriptor = NSSortDescriptor(key: "id", ascending: false)
fetchRequest.sortDescriptors = [sortDescriptor]

let result = try context.fetch(fetchRequest)
    for result in result {
        goalsArray.append(result)
        print("Fetched result goaltitle is \(result.goalTitle!)")
    }
    tableView.reloadData()

print("I've fetched the results")
}
catch {
    fatalError("Sthh")
    }
}



func countCoreDataObjects()-> Bool{
           //let request = NSFetchRequest<Goals>(entityName:"Goals")
    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

    do{
        let fetchRequest : NSFetchRequest<Goals> = Goals.fetchRequest() as! NSFetchRequest<Goals>
        let result = try context.fetch(fetchRequest)
        if result.count == 0 {
            return false
        } else {return true

        }
    }
    catch {
        fatalError("Sthh")
    }

}


func saveToCD(object: goalClassForPassing){

    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    let entity = NSEntityDescription.entity(forEntityName: "Goals", in: context)
    let goal = NSManagedObject(entity: entity!, insertInto: context) as! Goals



    goal.goalTitle = object.goalName
    goal.id = String(describing:Date())
    goal.imagePath = object.imagePath

    do {
        try context.save()}
    catch {
        fatalError("couldn't save to core data")
    }


    goal.id = String(describing: Date())
    goalObjectToSaveToCD?.id = String(describing: NSDate())
    print(goalObjectToSaveToCD?.goalTitle)
    print("Saved \(goal.goalTitle) - \(goal.id) - \(goal.imagePath) to Core Data")
    loadCoreData()
}

CoreData 实现 swift 3

CoreData implementation swift 3

swift

core-data

nsfetchrequest