Swift 3 核心数据删除对象 [英] Swift 3 Core Data Delete Object

问题描述

不幸的是，新的 Core Data 语义让我发疯了.我之前的问题有一个干净的代码，由于头文件的自动生成不正确而无法工作.现在我继续删除对象.我的代码似乎很简单:

Unfortunately the new Core Data semantics make me crazy. My previous question had a clean code that didn't work because of incorrect auto generation of header files. Now I continue my work with deleting objects. My code seems to be very simple:

func deleteProfile(withID: Int) {
    let fetchRequest: NSFetchRequest<Profile> = Profile.fetchRequest()
    fetchRequest.predicate = Predicate.init(format: "profileID==(withID)")
    let object = try! context.fetch(fetchRequest)
    context.delete(object)
} 

我使用 print(object) 而不是 context.delete(object) 进行了硬"调试，它向我展示了正确的对象.所以我只需要删除它.

I did a "hard" debug with print(object) instead of context.delete(object) and it showed me the right object. So I need just to delete it.

附言没有 deleteObject.现在 NSManagedContext 只有 public func delete(_ sender: AnyObject?)

P.S. there is no deleteObject. Now NSManagedContext has only public func delete(_ sender: AnyObject?)

推荐答案

获取的结果是一个 array 托管对象，在您的情况下[Event]，所以你可以枚举数组并删除所有匹配的对象.示例(使用 try? 而不是 try! 以避免崩溃获取错误):

The result of a fetch is an array of managed objects, in your case [Event], so you can enumerate the array and delete all matching objects. Example (using try? instead of try! to avoid a crash in the case of a fetch error):

if let result = try? context.fetch(fetchRequest) {
    for object in result {
        context.delete(object)
    }
}

如果不存在匹配的对象，则获取成功，但结果数组为空.

If no matching objects exist then the fetch succeeds, but the resulting array is empty.

注意:在您的代码中，object 具有 [Event] 类型，因此在

Note: In your code, object has the type [Event] and therefore in

context.delete(object)

编译器创建一个调用

public func delete(_ sender: AnyObject?)

NSObject 的方法而不是预期的

public func delete(_ object: NSManagedObject)

NSManagedObjectContext 的方法.这就是你的代码编译的原因但在运行时失败.

method of NSManagedObjectContext. That is why your code compiles but fails at runtime.

这篇关于Swift 3 核心数据删除对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！