ios - Xcode 6.0 Swift，出现错误 : can't evoke'! =' with an argument list

Question

在 Swift 语言最终确定并且我将 Xcode 更新到最新版本后，我用 Swift 编写的程序报告了一堆错误。我仍然无法解决的问题是“无法唤起”!=”类型为“(NSPersistentStoreCoordinator, NiLiteralConvertible)”的参数列表

代码在应用程序委托(delegate)类中，我试图在这里实现核心数据。

import UIKit
import CoreData
import Foundation

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?


func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool {
    // Override point for customization after application launch.
    return true
}

func applicationWillResignActive(application: UIApplication) {
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}

func applicationDidEnterBackground(application: UIApplication) {
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

func applicationWillEnterForeground(application: UIApplication) {
    // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}

func applicationDidBecomeActive(application: UIApplication) {
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

func applicationWillTerminate(application: UIApplication) {
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
    self.saveContext()
}
func saveContext () {
    var error: NSError? = nil
    let managedObjectContext = self.managedObjectContext
    if (_managedObjectContext != nil) {
        if managedObjectContext.hasChanges && !managedObjectContext.save(&error) {
            // Replace this implementation with code to handle the error appropriately.
            // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            //println("Unresolved error \(error), \(error.userInfo)")
            abort()
        }
    }
}

// #pragma mark - Core Data stack

// Returns the managed object context for the application.
// If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
var managedObjectContext: NSManagedObjectContext {

if !(_managedObjectContext != nil) {

    let coordinator = self.persistentStoreCoordinator

    if coordinator != nil {   

//This is where the error was reported. 

    _managedObjectContext = NSManagedObjectContext()
    _managedObjectContext!.persistentStoreCoordinator = coordinator
    }

    }
    return _managedObjectContext!
}
var _managedObjectContext: NSManagedObjectContext? = nil

// Returns the managed object model for the application.
// If the model doesn't already exist, it is created from the application's model.
var managedObjectModel: NSManagedObjectModel {
if !(_managedObjectModel != nil) {
    let modelURL = NSBundle.mainBundle().URLForResource("InTheDark", withExtension: "momd")
    _managedObjectModel = NSManagedObjectModel(contentsOfURL: modelURL!)
    }
    return _managedObjectModel!
}
var _managedObjectModel: NSManagedObjectModel? = nil

// Returns the persistent store coordinator for the application.
// If the coordinator doesn't already exist, it is created and the application's store added to it.
var persistentStoreCoordinator: NSPersistentStoreCoordinator {
if !(_persistentStoreCoordinator != nil) {
    let storeURL = self.applicationDocumentsDirectory.URLByAppendingPathComponent("InTheDark.sqlite")
    var error: NSError? = nil
    _persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
    if _persistentStoreCoordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: storeURL, options: nil, error: &error) == nil {


        abort()
    }
    }
    return _persistentStoreCoordinator!
}
var _persistentStoreCoordinator: NSPersistentStoreCoordinator? = nil

// #pragma mark - Application's Documents directory

// Returns the URL to the application's Documents directory.
var applicationDocumentsDirectory: NSURL {
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
    return urls[urls.endIndex-1] as NSURL
}


}

有人可以帮帮我吗？非常感谢。

Answer 1

由于 persistentStoreCoordinator 被声明为 NSPersistentStoreCoordinator，而不是 NSPersistentStoreCoordinator? 或 NSPersistentStoreCoordinator!，它不能是 nil。因此，您不能将它与 nil 进行比较。您可以去掉 nil 检查，或更改 persistentStoreCoordinator 的类型以 ? 或 ! 结尾。