Question

我在AppDelegate之外创建了一个单独的CoreDataStack.swift对象，以便在使用CoreData时遵循此处的大部分建议。但是如何将MOC传递给AppDelegate中的rootViewController？我是否需要将代码添加到AppDelegate或ViewController？感谢任何可以在Swift帮助我的人，因为较旧的ObjC对我不起作用！

我的CoreDataStack包含MOC

  lazy var managedObjectContext: NSManagedObjectContext = {
let managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType) //
managedObjectContext.persistentStoreCoordinator = self.persistentStoreCoordinator
return managedObjectContext
}()

AppDelegate有一个创建一些数据的方法，在didFinishLaunchingWithOptions中我可以打印到控制台看它的工作

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

    let fetchRequest = NSFetchRequest(entityName: "WordList")
    do {
        let results = try coreDataStack.managedObjectContext.executeFetchRequest(fetchRequest)
        if results.count == 0 {
            addTestData()
        }

    } catch {
        fatalError("Error fetching data!")
    }

    do {
        if let results = try coreDataStack.managedObjectContext.executeFetchRequest(fetchRequest) as? [NSManagedObject] { //cast to an array of NSManagedObject
            for result in results {
                if let listName = result.valueForKey("listName") as? String {
                    print("Got a '\(listName)'")
                }
            }
        }
    } catch {
        print("There was a fetch error")
    }

// WHAT CODE HERE WILL PASS THE MOC TO THE ROOT VC?

return true
}

我在导航控制器中嵌入了一个简单的TableViewController

import UIKit
import CoreData

class WordListsTableViewController: UITableViewController {

var coreDataStack: CoreDataStack!
var wordLists = [WordList]()

override func viewDidLoad() {
    super.viewDidLoad()

    title = "Word Lists"
    navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem:    .Add, target: self, action: "viewWordList")
}

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)

//  DO I NEED CODE HERE TO CALL THE MOC?

    reloadData()
    tableView.reloadData()
}

func reloadData() {
    let fetchRequest = NSFetchRequest(entityName: "WordList")

    do {
        if let results = try coreDataStack.managedObjectContext.executeFetchRequest(fetchRequest) as? [WordList] {
            wordLists = results
        }
    } catch {
        fatalError("There was an error fetching wordLists!")
    }
}

Answer 1

有多种方法可以访问托管对象上下文。如果您在AppDelegate中定义了managedObjectContext，则可以使用：

let appDelegate = UIApplicationDelegate.sharedApplication().delegate as! AppDelegate
let managedObjectContext = appDelegate.managedObjectContext
managedObjectContext.doStuff()

通过视图控制器传递managedObjectContext的第二种方法是创建UIViewController的扩展名。

extension UIViewController {
    lazy var managedObjectContext: NSManagedObjectContext {
        // Create core data stack or use singleton object
        return coreDataStack.managedObjectContext
    }
}

通过这样做，可以访问UIViewController的每个子类上的managedObjectContext。然后你可以写：

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    self.managedObjectContext.doSomething()
}

通过以上任何方式访问managedObjectContext，您可以在managedObjectContext和您创建的任何rootViewController中获得UIViewController。

如何在Swift中将ManagedObjectContext传递给根视图控制器

1 个答案: