ios - swift 核心数据 : How to fetch all items in array?

Question

我想删除我的 NSManagedObject Weather 和 Currently 的现有内容。

let entityNames = ["Weather", "Currently"]
for entityName in entityNames {
    let fetchRequest = NSFetchRequest(entityName: entityName)
    let objects = try(context.execute(fetchRequest)) as? [NSManagedObject]
    for object in objects! {
        context.deletedObjects(object)
    }
}

但是使用此代码时，我在第 3 行收到错误消息:

Generic parameter 'ResultType' could not be inferred

Answer 1

您必须指定获取请求的通用类型

let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: entityName)

那么你甚至可以省略结果类型

let objects = try? context.execute(fetchRequest)

还有一个错别字。你可能是说

context.deleteObject(object)

在 macOS 10.11+/iOS 9.0+ 中，我们鼓励您使用 NSBatchDeleteRequest