Swift CoreData:错误:无法在 NSManagedObject 类“NSManagedObject"上调用指定的初始值设定项 [英] Swift CoreData: error: Failed to call designated initializer on NSManagedObject class 'NSManagedObject'

问题描述

我正在使用核心数据在 vc1 中保存一个类别，并希望将列表属性添加到 vc2 中的列表中.我的数据模型是许多列表属性的一个类别.

I'm using core data to save a category in vc1 and want to add list properties to a list in vc2. My data model is one category to many list properties.

我正在 vc1 中添加这样的类别:

I'm adding the category like this in vc1:

func createNewCategory() {
    var category: NSManagedObject! = NSEntityDescription.insertNewObjectForEntityForName("Category", inManagedObjectContext: self.context) as NSManagedObject
    category.setValue(self.categoryTextField.text, forKey: "name")

    var error: NSError? = nil
    self.context.save(&error)
}

在vc2中设置数据:

func setupCoreData() {
    var appDelegate: AppDelegate = (UIApplication.sharedApplication()).delegate as AppDelegate
    self.context = appDelegate.managedObjectContext!

    var request: NSFetchRequest = NSFetchRequest(entityName: "Category")
    if (self.context.executeFetchRequest(request, error: nil)) {
        var error: NSError? = nil
        self.listData = self.context.executeFetchRequest(request, error: &error)
        self.managedObject = self.listData.objectAtIndex(0) as NSManagedObject
    }
}

它在最后一行崩溃:self.managedObject = ... 说:

It crashes on the last row: self.managedObject = ... saying:

CoreData: error: Failed to call designated initializer on NSManagedObject class 'NSManagedObject' 

如果我放置一个断点并打印数组，则托管对象在数组中.怎么了?

The managed object is in the array if I put a break point and print the array. What's wrong?

推荐答案

专用初始化器是

class func insertNewObjectForEntityForName(_ entityName: String!,
   inManagedObjectContext context: NSManagedObjectContext!) -> AnyObject!

显然，您不是在插入新对象，因此您确实需要一个可选值.也许您将类变量 managedObject 声明为 NSManagedObject!?尝试将其设置为 NSManagedObject? 并将运算符更改为 as?.

Clearly, you are not inserting a new object, so you really want an optional value. Maybe you declared your class variable managedObject as NSManagedObject!? Try setting it to NSManagedObject? and also change the operator to as?.

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