iOS Swift中CoreData图片删除失败求助：无报错但数据未删除

我的CoreData包含Photos和Folder两个实体，Folder与Photos是一对多关系（一个文件夹可包含多张图片）。Photos的image属性为Binary Data类型，Folder的folderName属性为String类型。目前图片的保存与查询功能正常，但删除图片操作无报错却未真正删除CoreData中的数据。

DataManager类代码 #

class DataManager {
static let shared = DataManager()
lazy var persistentContainer: NSPersistentContainer = {
    let container = NSPersistentContainer(name: "CoreDataRelationship")
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
        if let error = error as NSError? {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    })
    return container
}()


func folder(name: String) -> Folder {
    let folder = Folder(context: persistentContainer.viewContext)
    folder.folder_name = name
    return folder
}


func photo(image: [UIImage], folder: Folder) -> Photos {
    let photo = Photos(context: persistentContainer.viewContext)
    
    let myImagesDataArray = convertImageToData(myImagesArray: image)
    //to store array of images using encoding
    var images: Data?
    do {
        images = try NSKeyedArchiver.archivedData(withRootObject: myImagesDataArray, requiringSecureCoding: true)
    } catch {
        print("error")
    }
    photo.setValue(images, forKeyPath: "image")
    folder.addToPhotos(photo)
    return photo
}


func folders() -> [Folder] {
    let request: NSFetchRequest<Folder> = Folder.fetchRequest()
    var fetchedFolders: [Folder] = []
    
    do {
        fetchedFolders = try persistentContainer.viewContext.fetch(request)
    } catch let error {
        print("Error fetching folders \(error)")
    }
    return fetchedFolders
}

func photos(folder: Folder) -> [UIImage]  {
    var imageDataArray = [Data]()
    var myImagesdataArray = [Data]()
    let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "Photos")
    fetchRequest.predicate = NSPredicate(format: "folder = %@", folder)
    do {
        let result = try persistentContainer.viewContext.fetch(fetchRequest)
        for data in result {
         imageDataArray.append(data.value(forKey: "image") as! Data)
      }
    } catch let error as NSError {
      print("Could not fetch. \(error), \(error.userInfo)")
    }
    //fetch image using decoding
    imageDataArray.forEach { (imageData) in
      var dataArray = [Data]()
        dataArray = unarchiveDocument(unarchivedObject: imageData)//try NSKeyedUnarchiver.unarchivedObject(ofClass: NSArray.self, from: imageData) as! [Data]
          myImagesdataArray.append(contentsOf: dataArray)
    }
    
    let imagesArray = convertDataToImages(imageDataArray: myImagesdataArray)
    return imagesArray
}

//Core Data Saving support
func save (){
    let context = persistentContainer.viewContext
    if context.hasChanges {
        do {
            try context.save()
        } catch {
            let nserror = error as NSError
            fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
        }
    }
}
func deletePhoto(photo: Photos) {
    let context = persistentContainer.viewContext
    context.delete(photo)
    save()
}

func deleteFolder(folder: Folder) {
    let context = persistentContainer.viewContext
    context.delete(folder)
    save()
}


func convertImageToData(myImagesArray: [UIImage]) -> [Data] {
    var myImagesDataArray = [Data]()
    myImagesArray.forEach({ (image) in
        myImagesDataArray.append(image.pngData()!)
    })
    return myImagesDataArray
}

func convertDataToImages(imageDataArray: [Data]) -> [UIImage] {
  var myImagesArray = [UIImage]()
  imageDataArray.forEach { (imageData) in
      myImagesArray.append(UIImage(data: imageData)!)
  }
  return myImagesArray
}

func unarchiveDocument(unarchivedObject:Data) -> [Data] {
    do {
        if let document = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(unarchivedObject) as? [Data] {
            return document
        }
    } catch {
        // do something with the error
    }
    return []
} }

删除操作代码 #

@objc func deleteTapped(_ sender: UIBarButtonItem) {
    var deleteNeededIndexPath: [IndexPath] = []
    for(key,value) in dictionarySelctedIndexPath {
        if value {
            deleteNeededIndexPath.append(key)
        }
    }
    
    for i in deleteNeededIndexPath {
        let photo = photos[i.item]
        photoTobeDelete.append(photo)
    }
        var deletedPhoto = DataManager.shared.photo(image: photoTobeDelete, folder: folder!)
        DataManager.shared.deletePhoto(photo: deletedPhoto)
    
        collectionView.deleteItems(at: deleteNeededIndexPath)
        dictionarySelctedIndexPath.removeAll()
}

问题根源与修复方案 #

问题核心 #

你在删除逻辑中犯了致命错误：没有删除CoreData中已存在的Photos实体，而是新建了一个完全无关的Photos实例去执行删除。

看这段错误代码：

var deletedPhoto = DataManager.shared.photo(image: photoTobeDelete, folder: folder!)
DataManager.shared.deletePhoto(photo: deletedPhoto)

调用photo(image:folder:)会在CoreContext中创建全新的Photos对象，你删除的是这个新对象，而非CoreData中原本存储的、对应选中图片的实体。

修复步骤 #

1. 新增获取Photos实体的方法
   在DataManager中添加方法，直接返回CoreData中的Photos实体引用，而非仅返回UIImage：

func fetchPhotoEntities(for folder: Folder) -> [Photos] {
    let fetchRequest: NSFetchRequest<Photos> = Photos.fetchRequest()
    fetchRequest.predicate = NSPredicate(format: "folder = %@", folder)
    do {
        return try persistentContainer.viewContext.fetch(fetchRequest)
    } catch let error {
        print("Error fetching photo entities: \(error)")
        return []
    }
}

2. 在视图控制器中保存实体引用
   新增数组存储Photos实体，确保和UI展示的图片一一对应：

// 视图控制器中新增属性
var photoEntities: [Photos] = []

// 加载数据时同时获取实体
photoEntities = DataManager.shared.fetchPhotoEntities(for: folder!)
photos = DataManager.shared.photos(folder: folder!)

3. 修正删除逻辑
   直接从photoEntities中获取要删除的CoreData实体，执行删除：

@objc func deleteTapped(_ sender: UIBarButtonItem) {
    var deleteNeededIndexPath: [IndexPath] = []
    for(key,value) in dictionarySelctedIndexPath {
        if value {
            deleteNeededIndexPath.append(key)
        }
    }
    
    // 按倒序删除，避免索引错乱
    for indexPath in deleteNeededIndexPath.sorted(by: { $0.item > $1.item }) {
        let targetEntity = photoEntities[indexPath.item]
        DataManager.shared.deletePhoto(photo: targetEntity)
        // 同步更新本地数组
        photoEntities.remove(at: indexPath.item)
        photos.remove(at: indexPath.item)
    }
    
    collectionView.deleteItems(at: deleteNeededIndexPath)
    dictionarySelctedIndexPath.removeAll()
}

额外优化建议 #

• 替换setValue(forKeyPath:)为直接属性访问：photo.image = images，提升代码安全性和可读性。
• 处理pngData()可能返回nil的情况，避免强制解包导致崩溃。
• 删除操作后可重新拉取数据，确保UI与CoreData状态完全同步。

内容的提问来源于stack exchange，提问作者Asim Iftikhar Abbasi