我想将数据存储到两个 viewControllers
的两个 coredata 实体中。
我可以实现这一目标,但是从单个viewController
来实现。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
{
}
}
}
您可以在上面的代码中看到,我有两个 coredata 实体PhoneContacts
和EmailContacts
。我可以将数据存储到两个viewController
的两个实体中。它有效。
现在,我想要的是,如何将数据存储到 viewController
1和entity2( EmailContacts
)的 viewController
2?
PhoneContacts
)中我应该将managedObjectContext
与第二个ViewController共享?或其他任何更好的解决方案都被接受。
我正在使用Xcode 8.2,Swift 3.0
预先感谢。
创建并使用单身顿类作为核心操作。
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Swift3。但是我写了这个答案,以了解我们如何做到。
我在两个不同的vc中使用这两个实体没有任何问题。
您要做的就是使用另一个VC中的以下两行:
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
然后您可以使用:
let emailContactRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "EmailContacts")
emailContactRequest.returnsObjectsAsFaults = false
let emailContactObject = NSEntityDescription.insertNewObject(forEntityName: "EmailContacts", into: context)
emailContactObject.setValue("Peter@gmail.com", forKey: "email")
emailContactObject.setValue("Peter", forKey: "emailname")
然后,您可以保存上下文&amp;使用您现在使用的相同方法来获取刚刚插入db中的第二个对象。
希望我有意义。
编辑:
就@raki所建议的那样,我个人更喜欢创建核心数据经理Singleton类。