ios - 如何在 Swift 中使用来自不同 View Controller 的多个核心数据实体

Question

我想将来自两个 viewControllers 的数据存储到两个 CoreData 实体中。

我可以实现这一点，但是来自单个 viewController。通过使用以下代码。

import UIKit
import CoreData
class ViewController: UIViewController {

    override func viewDidLoad()
    {

        let appDelegate = UIApplication.shared.delegate as! AppDelegate

        let context = appDelegate.persistentContainer.viewContext

        let phoneContactRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "PhoneContacts")

        phoneContactRequest.returnsObjectsAsFaults = false

        let emailContactRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "EmailContacts")

        emailContactRequest.returnsObjectsAsFaults = false
        /*
         // Save to database 

         //object one
         let phoneContactsObject = NSEntityDescription.insertNewObject(forEntityName: "PhoneContacts", into: context)

            phoneContactsObject.setValue("John", forKey: "name")
        phoneContactsObject.setValue("8335636532", forKey: "number")

         //object two
        let emailContactObject = NSEntityDescription.insertNewObject(forEntityName: "EmailContacts", into: context)
        emailContactObject.setValue("Peter@gmail.com", forKey: "email")
        emailContactObject.setValue("Peter", forKey: "emailname")
         */


        do{

            // Fetch from PhoneContacts entity
            let phoneContactResults = try context.fetch(phoneContactRequest)

            if phoneContactResults.count > 0
            {
                for phoneContactResult in phoneContactResults as! [NSManagedObject]
                {
                    if let phoneContactName = phoneContactResult.value(forKey: "name")
                    {
                        print(phoneContactName)
                    }
                    if let phoneContactNumber = phoneContactResult.value(forKey: "number")
                    {
                        print(phoneContactNumber)
                    }
                }
            }
            // Fetch from EmailContacts entity
            let emailContactResults = try context.fetch(emailContactRequest)

            if emailContactResults.count > 0
            {
                    for emailContactResult in emailContactResults as! [NSManagedObject]
                    {
                        if let emailContactName = emailContactResult.value(forKey: "emailname")
                        {
                            print(emailContactName)
                        }
                        if let emailContactEmail = emailContactResult.value(forKey: "email")
                        {
                            print(emailContactEmail)
                        }
                    }
                }
        }
        catch
        {            
        }        
    }    
}

正如您在上面的代码中看到的，我有两个 CoreData 实体 PhoneContacts 和 EmailContacts。我可以将数据从单个 viewController 存储到两个实体中。它有效。

现在，我想要的是，如何将数据存储到 viewController 1 的 entity1(PhoneContacts) 和来自 entity2(EmailContacts) viewController 2 ?

我应该将 managedObjectContext 共享给第二个 viewController 吗？或者接受任何其他更好的解决方案。

我正在使用 Xcode 8.2、Swift 3.0

提前致谢。

Answer 1

为 CoreData 操作创建并使用单例类。

例如

class CoreDataHelper: NSObject
{
   static let sharedInstance = CoreDataHelper()

   func appDelegate()->AppDelegate
   {
     return UIApplication.sharedApplication().delegate as! AppDelegate
   }

   func managedObjectContext() -> NSManagedObjectContext
   {
     return self.appDelegate().managedObjectContext
   }
   func fetchPhoneContacts() -> [NSManagedObject]
   {
      // write code to fetch contacts from PhoneContacts entity
   }
   func fetchEmailContacts() -> [NSManagedObject]
   {
      // write code to fetch contacts from EmaliContacts entity
   }
}

来自 viewController1

let phoneContatcs = CoreDataHelper.sharedInstance().fetchPhoneContacts()

来自 viewController2

let emailContatcs = CoreDataHelper.sharedInstance().fetchEmailContacts()

注意:我知道问题是针对 Swift3 的。但我写这个答案是为了让我们知道如何做到这一点。