删除核心数据中的第一个对象（快速） [英] Deleting first object in Core Data (Swift)

问题描述

我正在请求Core Data根据contentid以升序返回我的Entity条目：

I am requesting Core Data to return me its Entity entries in ascending order based on contentid:

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

let sort = NSSortDescriptor(key:"contentid", ascending:true)
fetchRequest.sortDescriptors = [sort]

let fetchedResults = managedObjectContent.executeFetchRequest(fetchRequest, error: &error) as! [NSManagedObject]

如何删除Core Data返回的，升序的条目中的第一个对象？

How do I delete the first object in Core Data's returned, ascending entries?

我还尝试通过指定以下内容来获取单个对象：

I have also tried getting a single object by specifying:

fetchRequest.fetchLimit = 1

我认为这样做会返回[NSManagedObject]，因此尝试执行以下操作：

Thinking that this would return an [NSManagedObject], I attempted to then perform:

managedObjectContext.deleteObject(fetchedResults)

但是它引发了错误：无法调用类型为'（[NSManagedObject]）'的方法deleteObject。我到底在做什么错？我是否需要将 [NSManagedObject] 转换为 NSManagedObject ？

But it threw the error: cannot invoke method deleteObject with type '([NSManagedObject])'. What exactly am I doing incorrectly? Do I need to convert [NSManagedObject] to NSManagedObject, perhaps?

推荐答案

尝试一下：

let fetchedResults = context.executeFetchRequest(fetchRequest, error: nil)
if let result = fetchedResults?.first as? NSManagedObject {
    context.deleteObject(result)
}

executeFetchRequest 返回 [AnyObject]？，因此您必须将其拆开，取出第一个对象并将其转换为 NSManagedObject 。之后，您将可以对该对象执行删除操作。

executeFetchRequest returns [AnyObject]? so you must unwrap it, take first object and cast it to NSManagedObject. After that you will be able to perform delete with this object.

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