Question

发生了什么：我是swift的新手，我还不太了解CoreData，但我在youtube上关注了一些教程，所以我可以学习它。现在，当我运行我的应用程序时，它崩溃，然后出现错误＆＃34;致命错误：在展开可选值时意外发现nil＆＃34;

详细信息：此代码来自一个帮助新人快速使用CoreData的教程。

以下是代码：

导入UIKit 导入CoreData

类SwiftCoreDataHelper：NSObject {

class func directoryForDatabaseFilename()->NSString{
    return NSHomeDirectory().stringByAppendingString("/Library/Private Documents")
}


class func databaseFilename()->NSString{
    return "database.sqlite";
}


class func managedObjectContext()->NSManagedObjectContext{

    var error:NSError? = nil

    NSFileManager.defaultManager().createDirectoryAtPath(SwiftCoreDataHelper.directoryForDatabaseFilename() as String, withIntermediateDirectories: true, attributes: nil, error: &error)

    let path:NSString = "\(SwiftCoreDataHelper.directoryForDatabaseFilename()) + \(SwiftCoreDataHelper.databaseFilename())"

    let url:NSURL = NSURL(fileURLWithPath: path as String)!

    let managedModel:NSManagedObjectModel = NSManagedObjectModel.mergedModelFromBundles(nil)!

    var storeCoordinator:NSPersistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: managedModel)

    if !(storeCoordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil, error:&error ) != nil){
        if (error != nil){
            println(error!.localizedDescription)
            abort()
        }
    }

    var managedObjectContext = NSManagedObjectContext(concurrencyType: NSManagedObjectContextConcurrencyType.MainQueueConcurrencyType)

    managedObjectContext.persistentStoreCoordinator = storeCoordinator

    return managedObjectContext


}

class func insertManagedObject(className:NSString, managedObjectConect:NSManagedObjectContext)->AnyObject{

    let managedObject:NSManagedObject = NSEntityDescription.insertNewObjectForEntityForName(className as String, inManagedObjectContext: managedObjectConect) as! NSManagedObject

    return managedObject

}

class func saveManagedObjectContext(managedObjectContext:NSManagedObjectContext)->Bool{
    if managedObjectContext.save(nil){
        return true
    }else{
        return false
    }
}


class func fetchEntities(className:NSString, withPredicate predicate:NSPredicate?, managedObjectContext:NSManagedObjectContext)->NSArray{
    let fetchRequest:NSFetchRequest = NSFetchRequest()
    let entetyDescription:NSEntityDescription = NSEntityDescription.entityForName(className as String, inManagedObjectContext: managedObjectContext)!

    fetchRequest.entity = entetyDescription
    if (predicate != nil){
        fetchRequest.predicate = predicate!
    }

    fetchRequest.returnsObjectsAsFaults = false
    let items:NSArray = managedObjectContext .executeFetchRequest(fetchRequest, error: nil)!

    return items
}

}

然后，它在这里崩溃了：

    **let entetyDescription:NSEntityDescription = NSEntityDescription.entityForName(className as String, inManagedObjectContext: managedObjectContext)!** // Crashes right here, "Thead 1: EXC_BAD_INSTRUCTION(code=EXC_I386_INVOP,subcode=0x0)

我该怎么做才能解决这个错误？我在这个帖子里待了3天，我不知道在哪里跑！

提前致谢。

更新

这是我的代码：

导入UIKit 导入CoreData

类MainViewController：UIViewController，UITableViewDataSource，UITableViewDelegate {

@IBOutlet weak var mainImage: UIImageView!
@IBOutlet weak var tableView: UITableView!
var namesListArray:NSMutableArray = NSMutableArray()



override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)
    loadData()
}

func loadData() {
    namesListArray.removeAllObjects()
    let moc:NSManagedObjectContext = SwiftCoreDataHelper.managedObjectContext()
    let results:NSArray = SwiftCoreDataHelper.fetchEntities(NSStringFromClass(Recipe), withPredicate: nil, managedObjectContext: moc)
    for recipe in results {
        let singleRecipe:Recipe = recipe as! Recipe
        let recipeDict:NSDictionary = ["identifier":singleRecipe.identifier, "recipelabel":singleRecipe.recipelabel, "recipeimage":singleRecipe.recipeimage]
        namesListArray.addObject(recipeDict)
    }
    tableView.reloadData()     }

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return namesListArray.count
}

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    let cell:CustomCellTableViewCell = tableView.dequeueReusableCellWithIdentifier("customCell", forIndexPath: indexPath) as! CustomCellTableViewCell
    let recipeDict:NSDictionary = namesListArray.objectAtIndex(indexPath.row) as! NSDictionary
    let recipeName = recipeDict.objectForKey("recipelabel") as! String
    let imageData:NSData = recipeDict.objectForKey("recipeimage") as! NSData
    let recipeImage: UIImage = UIImage(data: imageData)!
    cell.customLabel.text = recipeName
    var recipeImageFrame:CGRect = cell.customImage.frame
    recipeImageFrame.size = CGSizeMake(75,75)
    cell.customImage.frame = recipeImageFrame
    cell.customImage.image = recipeImage

    return cell
}

}

谓词NSPredicate？无无

也许错误在这附近？如果是这样，我无法看到它。有什么想法吗？

再次感谢!!!

Answer 1

传递的className很可能在其中有拼写错误，因此您无法从模型中检索实体。将传入的内容与模型所期望的内容进行比较，您将发现错误。

更新

在该方法中打印出className。打印出来的是什么？它与模型中的相匹配吗？类名很少与实体名相同。

Answer 2

我有类似的错误。对我有用的是，在您的实体'食谱'中尝试添加以下内容

@objc（配方） class Recipe：NSManagedObject { ... }

您正在将Recipe暴露给Objective-C。我正在使用Xcode 7.3.1。

还有一件事需要检查。确保在数据模型检查器中具有您的模块字段是空白的。要到达那里，请单击.xcdatamodelId并在右侧窗格中单击。

NSEntityDescription在展开可选值

2 个答案:

更新