从“NSPersistentStoreResult”投射到不相关类型“实体”始终失败 [英] Casting from 'NSPersistentStoreResult' to unrelated type 'Entity' always fails

问题描述

我正在创建一个小应用程序，以了解CoreData中的多对多关系。但是使用下面的代码，我得到一个错误从我的NSFetchResult转换到我的Entity类（'Groepering'）：

I am creating a small app to learn the many to many relationships in CoreData. However using the code below I get an error casting from my NSFetchResult to my Entity class ('Groepering'):

与我的项目相比，我在互联网上发现的样本没有什么区别，为什么演员仍然失败？

I do not see any difference from samples I found on the internet compared to my project, why does the cast still fail?

let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext

let fetchRequest : NSFetchRequest = NSFetchRequest(entityName: "Entity")

    do {
        let fetchResults = try managedContext.executeRequest(fetchRequest)
        let groeperingen = fetchResults as! [Entity]
        // Here I get the Error: ^

    } catch {
        print("Error")
}

推荐答案

使用NSManagedObjectContext的 executeFetchRequest 执行NSFetchRequest。

Use executeFetchRequest method of NSManagedObjectContext when performing a NSFetchRequest.

编辑Swift 3 ：对于Swift 3，请使用：

Edit Swift 3: For Swift 3, use:

let result = try managedContext.fetch(fetchRequest)

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