Swift

Question

我已经在互联网上（主要是在这里）搜索了我的问题，我已经尝试过了，但我仍然无法让它工作。我正在尝试从核心数据中检索图像，然后将其显示在 table 视图中。所以基本上，一个 table 视图带有缩略图以及名称和开关。我下面有以下 swift 个文件。任何人都可以引导我做什么？除了图像检索之外，我还计划添加一个开关，当打开 on/off 时，它会要求输入密码，以便可以切换 on/off。我该如何开始呢？希望得到您的友好回应。谢谢！

我有这段代码用于将包含图像的记录保存到核心数据。

let mOC =
(UIApplication.sharedApplication().delegate
    as! AppDelegate).managedObjectContext

@IBOutlet weak var firstName: UITextField!
@IBOutlet weak var lastName: UITextField!
@IBOutlet weak var status: UILabel!

@IBAction func saveRecord(sender: AnyObject) {
    let entityDescription =
    NSEntityDescription.entityForName("Faculty",
        inManagedObjectContext: mOC)

    let faculty = Faculty(entity: entityDescription!,
        insertIntoManagedObjectContext: mOC)

    faculty.firstname = firstName.text
    faculty.lastname = lastName.text

    let pickedImage = UIImageJPEGRepresentation(imageView.image!, 1.0)

    faculty.image = pickedImage

    do {
        try mOC.save()
        firstName.text = ""
        lastName.text = ""

        status.text = "New record saved."
        NSNotificationCenter.defaultCenter().postNotificationName("load", object: nil)
        self.dismissViewControllerAnimated(true, completion: nil)
    } catch {
        status.text = "Record not saved."
    }

}

@IBOutlet weak var imageView: UIImageView!
var newMedia : Bool?
@IBAction func choosePhoto(sender: AnyObject) {
    if UIImagePickerController.isSourceTypeAvailable(
        UIImagePickerControllerSourceType.SavedPhotosAlbum) {
            let imagePicker = UIImagePickerController()

            imagePicker.delegate = self
            imagePicker.sourceType =
                UIImagePickerControllerSourceType.PhotoLibrary
            imagePicker.mediaTypes = [kUTTypeImage as String]
            imagePicker.allowsEditing = false
            self.presentViewController(imagePicker, animated: true,
                completion: nil)
            newMedia = false

    }

}

这是 TableViewController，它在 table 视图上显示记录，并且应该与图像一起显示，我正在尝试弄清楚。

let managedObjectContext =
(UIApplication.sharedApplication().delegate
    as! AppDelegate).managedObjectContext

var fetchedLastName = [String]()
var fetchedFirstName = [String]()

override func viewDidLoad() {
    super.viewDidLoad()

    NSNotificationCenter.defaultCenter().addObserver(self, selector: "reloadData:",name:"load", object: nil)

    let entityDescription =
    NSEntityDescription.entityForName("Faculty",
        inManagedObjectContext: managedObjectContext)

    let request = NSFetchRequest()
    request.entity = entityDescription

    do{
        let objects = try managedObjectContext.executeFetchRequest(request)

        let results = objects

        if results.count > 0 {
            for var i = 0; i < results.count; i += 1{
                let match = results[i] as! NSManagedObject

                fetchedLastName.append((match.valueForKey("lastname") as? String)!)
                fetchedFirstName.append((match.valueForKey("firstname") as? String)!)

            }
        } else {

        }
    }
    catch{}
}

func reloadData(notification: NSNotification){
    fetchedLastName.removeAll()
    fetchedFirstName.removeAll()

    let entityDescription =
    NSEntityDescription.entityForName("Faculty",
        inManagedObjectContext: managedObjectContext)

    let request = NSFetchRequest()
    request.entity = entityDescription

    do{
        let objects = try managedObjectContext.executeFetchRequest(request)

        let results = objects

        if results.count > 0 {
            for var i = 0; i < results.count; i += 1{
                let match = results[i] as! NSManagedObject

                fetchedLastName.append((match.valueForKey("lastname") as? String)!)
                fetchedFirstName.append((match.valueForKey("firstname") as? String)!)
            }
        } else {

        }
    }
    catch{}

    self.tableView.reloadData()
}

我认为我应该在此处的某处编写代码以从核心数据中检索图像并将其显示在 table 视图上，我的想法是否正确？

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("TEACH", forIndexPath: indexPath) as! TEACHTableViewCell

    let row = indexPath.row

    cell.facultyName.text = fetchedLastName[row] + ", " + fetchedFirstName[row]

    return cell
}

Answer 1

不太确定 Faculty() 包含什么，但是，您需要将图像作为 NSData 保存到 CoreData，然后当您想要从 CoreData 获取图像时，您需要 NSData 并将其转换为图像，如下所示：

let image = UIImage(named: "BackgroundSky")
//Change named: "" to your image
let imageAsNSData = UIImageJPEGRepresentation(image!, 1.0)

然后将其作为 NSData 保存到 CoreData，然后当您从 CoreData 取回它时，这就是将其转换为图像的方法：

let image = UIImage(data: imageAsNSData!)
//Change data: to the NSData

这就是从 UIImage 到 NSData 来回变化和图像的方式。

Answer 2

这样解决了：

var fetchedImage = [NSData]()

fetchedImage.append((match.valueForKey("image") as? NSData)!)

和

cell.facultyImage.image = fetchedImage[row]

Answer 3

好的，这是固定代码：

TeachTableViewController:

//
//  TEACHTableViewController.swift
//  TEACH
//
//  Created by ICST340.N1 on 9/29/15.
//  Copyright © 2015 IyoTugs. All rights reserved.
//

import UIKit
import CoreData

class TEACHTableViewController: UITableViewController {
let managedObjectContext =
(UIApplication.sharedApplication().delegate
    as! AppDelegate).managedObjectContext

var fetchedLastName = [String]()
var fetchedFirstName = [String]()
var fetchedImage = [UIImage]()

override func viewDidLoad() {
    super.viewDidLoad()

    NSNotificationCenter.defaultCenter().addObserver(self, selector: "reloadData:",name:"load", object: nil)

    let entityDescription =
    NSEntityDescription.entityForName("Faculty",
        inManagedObjectContext: managedObjectContext)

    let request = NSFetchRequest()
    request.entity = entityDescription

    do{
        let objects = try managedObjectContext.executeFetchRequest(request)

        let results = objects

        if results.count > 0 {
            for var i = 0; i < results.count; i += 1{
                let match = results[i] as! NSManagedObject

                fetchedLastName.append((match.valueForKey("lastname") as? String)!)
                fetchedFirstName.append((match.valueForKey("firstname") as? String)!)
                //added this is convert the image
                let image = match.valueForKey("image") as! NSData
                fetchedImage.append(UIImage(data: image)!)

            }
        } else {

        }
    }
    catch{}
    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = false

    // Uncommented this
    // Uncomment the following line to display an Edit button in the          navigation bar for this view controller.
    //        self.navigationItem.rightBarButtonItem = self.editButtonItem()
}

func reloadData(notification: NSNotification){
    fetchedLastName.removeAll()
    fetchedFirstName.removeAll()
    //Added this to remove all images
    fetchedImage.removeAll()

    let entityDescription =
    NSEntityDescription.entityForName("Faculty",
        inManagedObjectContext: managedObjectContext)

    let request = NSFetchRequest()
    request.entity = entityDescription

    do{
        let objects = try managedObjectContext.executeFetchRequest(request)

        let results = objects

        if results.count > 0 {
            for var i = 0; i < results.count; i += 1{
                let match = results[i] as! NSManagedObject

                fetchedLastName.append((match.valueForKey("lastname") as? String)!)
                fetchedFirstName.append((match.valueForKey("firstname") as? String)!)
                //added this is convert the image
                let image = match.valueForKey("image") as! NSData
                fetchedImage.append(UIImage(data: image)!)

            }
        } else {

        }
    }
    catch{}

    self.tableView.reloadData()
}


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

// MARK: - Table view data source

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
    // #warning Incomplete implementation, return the number of sections
    return 1
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // #warning Incomplete implementation, return the number of rows
    return fetchedLastName.count
}


override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("TEACH", forIndexPath: indexPath) as! TEACHTableViewCell

    let row = indexPath.row

    print(fetchedFirstName)

    cell.facultyName.text = fetchedLastName[row] + ", " + fetchedFirstName[row]
    cell.facultyImage.image = fetchedImage[row]

    return cell
}

}

我标记了我修复的每个点，但只有四个点。其中两个与获取 NSData 并将其转换为图像有关（在 viewDidLoad 和 reloadData 中，相同的位置）。其中之一是注释掉使右侧导航栏按钮成为编辑按钮的行。最后一个 fetchedImage.removeAll() 在 reloadData 的顶部取出所有图像。

Swift - 从核心数据中检索图像

Swift - Retrieving Image from Core Data

core-data

ios8

xcode7