ios - fatal error : unexpectedly found nil while unwrapping an Optional value inside an entity

Question

我希望在点击删除按钮时删除一个 UICollectionViewCell:

@IBAction func deleteButtonClicked() {

    error here:    delegate?.deleteTrigger(clothes!)

}

衣服:

var clothes: Clothes? {
        didSet {

            updateUI()
        }
    }

func deleteTrigger:

 func deleteTrigger(clothes: Clothes){

        let appDel: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate

        let context: NSManagedObjectContext = appDel.managedObjectContext!
        let en = NSEntityDescription.entityForName("Category", inManagedObjectContext: context)


        if let entity = NSEntityDescription.entityForName("Category", inManagedObjectContext: context) {



        let indexPath = NSIndexPath()

        //var cat : Category = clothing as! Category
        let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
        let managedContext: NSManagedObjectContext = appDelegate.managedObjectContext!
        let fetchRequest = NSFetchRequest(entityName: "Clothes")

        let predicate = NSPredicate(format: "category == %@", self.selectedCategory!)
        fetchRequest.predicate = predicate

        var error: NSError? = nil
        var clothesArray = managedContext.executeFetchRequest(fetchRequest, error: &error)!
        managedContext.deleteObject(clothesArray[indexPath.row] as! NSManagedObject)
        clothesArray.removeAtIndex(indexPath.row)
        self.collectionView?.deleteItemsAtIndexPaths([indexPath])

        if (!managedContext.save(&error)) {
            abort()


        }

        }

衣服是 Core Data 中的一个实体。有谁知道我为什么会收到此错误？我正在尝试从具有一对多关系的核心数据中删除 collectionViewCell。 Category 是父实体，Clothes 是 Category 中的实体。

Answer 1

你已经声明了一个属性衣服:

var clothes: Clothes?

您从未给它任何值，所以它是nil。因此，当您通过说 clothes! 强制打开它时，您会崩溃。