Question

您好我目前正在使用Swift教程，该教程使用旧版本的Swift，我无法遵循这一点，因为我相信在较新版本的Swift中语法已经改变。

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    var appDel:AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate

    var context:NSManagedObjectContext = appDel.managedObjectContext

    var newUser = NSEntityDescription.insertNewObjectForEntityForName("users", inManagedObjectContext: context) as NSManagedObject

    newUser.setValue("Joe", forKey: "username")

    newUser.setValue("pass", forKey: "password")

    do {
     try context.save()
    } catch let error {
        print("Couldn't save user data")
        print(error)
    }

    let request = NSFetchRequest(entityName: "Users")
        request.returnsObjectsAsFaults = false
      //  var results = context.executeFetchRequest(request)

    do {
        var results =
            try context.executeFetchRequest(request)
        results = results as! [NSManagedObject]
    } catch let error as NSError {
        print(error)
    }

    for result: AnyObject in results {
        print(results)
    }
}

我收到的错误与结果行上的结果有关：结果中的AnyObject和错误是未解析的标识符＆＃39;结果＆＃39;这给我的印象是，这应该在某处作为变量声明，因为它目前尚未解决，但我无法弄清楚如何解决这个问题，非常感谢任何帮助，谢谢！

Answer 1

do {
    var results = try context.executeFetchRequest(request)
    results = results as! [NSManagedObject]
} catch let error as NSError {
    print(error)
}

for result: AnyObject in results {
    print(results)
}

results只有do块内的范围。您需要在do：

中移动数组的处理

do {
    var results = try context.executeFetchRequest(request)
    results = results as! [NSManagedObject]
    for result in results {
        print(results)
    }
} catch let error as NSError {
    print(error)
}

此外，无需通过投射AnyObject来丢失信息。

Answer 2

使用针对CoreData的新API（在Swift 3.0中），你应该这样做：

let request = NSFetchRequest<Users>(entityName: "Users")
request.returnsObjectsAsFaults = false

do {
    var results =
        try context.fetch(request)
    // `results` will here be [Users]
} catch let error as NSError {
    print(error)
}

获取的新签名为fetch<T : NSFetchRequestResult>(_ request: NSFetchRequest<T>) throws -> [T]，其中T与<HERE>中提供的相同（例如NSFetchRequest<Users>）

核心数据问题Swift

2 个答案: