swift - 使用核心数据中的索引来获取特定的二进制数据

Question

下面的 swift 代码将 2 个单独的图像保存到核心数据中。我想要做的是，当用户在文本字段中输入 1 时，输入核心数据的第一张图像将出现在 imaegview 图片上。如果输入 2，第二张图像将出现在 ImageView 上。我的代码基于使用字符串而不是二进制数据。我在 pic.image = user.image 处收到编译错误，指出无法分配“数据”类型的值？输入“UIImage？”。 https://github.com/redrock34/be

 import UIKit
import CoreData


class ViewController: UIViewController,UITextFieldDelegate {


    @IBOutlet var labelName : UILabel!
    @IBOutlet var enterT : UITextField!
    @IBOutlet var pic : UIImageView!
    lazy var context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext


    var dx = [UIImage]()
    var names = [String]()

    override func viewDidLoad() {
        super.viewDidLoad()


        enterT.delegate = self

        pic.backgroundColor = .cyan


        guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
        let managedContext = appDelegate.persistentContainer.viewContext
        let entity = NSEntityDescription.entity(forEntityName: "Users", in: managedContext)!
        let item = NSManagedObject(entity: entity, insertInto: managedContext)
             let item2 = NSManagedObject(entity: entity, insertInto: managedContext)
        let fetch = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")

        let vex = UIImage(named: "on.jpg")?.pngData()
        if let data = vex{
            item.setValue(data, forKey: "image")

        }




        let vex2 = UIImage(named: "house.jpg")?.pngData()
        if let data2 = vex2{
            item2.setValue(data2, forKey: "image")
        }




             do {
                 let result = try? managedContext.fetch(fetch) as? [Users]
                 print("Queen",result?.count)
                 try? managedContext.save()



             }
             catch {
                 print("Could not save")
             }


    }


    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

        guard let text = (textField.text as? NSString)?.replacingCharacters(in: range, with: string), let index = Int(text) else { //here....
            // display an alert about invalid text
            return true
        }
        save(at: index )
        return true
    }

    func save(at index : Int) {
        let fetchRequest = NSFetchRequest<Users>(entityName: "Users")
        fetchRequest.predicate = NSPredicate(format: "idx == %d", Int32(index))
        do {
            if let user = try context.fetch(fetchRequest).first {
                pic.image = user.image
            }
        } catch {
            print("Could not fetch \(error) ")
        }
        return
    }

    @IBAction func add(){


        fetch()
    }

    func fetch()
    {



        for i in 0..<dx.count {
            let newUser = Users(context: context)
            newUser.username = names[i]
            newUser.idx = Int32(i + 1)


        }
        print("Storing Data..")
        do {
            try context.save()
        } catch {
            print("Storing data Failed", error)
        }
        return
    }


}

Answer 1

您需要将 Data 类型的图像转换为 UIImage，如下所示。

UIImage(data: user.image ?? Data())