Swift CoreData：error：无法调用NSManagedObject类的指定初始化器'NSManagedObject' [英] Swift CoreData: error: Failed to call designated initializer on NSManagedObject class 'NSManagedObject'

问题描述

我使用核心数据来保存vc1中的类别，并希望将列表属性添加到vc2中的列表。我的数据模型是一个类别到许多列表属性。

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.

我在vc1中添加如下类别：

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)
}

设置vc2中的数据：

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
    }
}

最后一行崩溃： self.managedObject = .. 。说：

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，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

专用初始化程序为

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

显然，你没有插入一个新的对象，所以你真的想要一个可选的值。也许你已经将你的类变量 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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