今天我们来通过创建一个小的Demo来实践我们的CoreDate 的学习。参考书籍Core_Data_by_Tutorials
更多关于CoreDate的基础知识
创建Core Data Stack
主要一下几个步骤:
NSManagedObjectModel
NSPresistentStore
NSPersistentStoreCoordinator
NSManagedObjectContext
在这里就不多说每一个都是什么了,可以参考上边给出的两篇博客
Show your code
- import CoreData
- class CoreDadaStack {
- /// model Name
- private let modelName = "Dog Walk"
- /// Document Directory URL
- private lazy var applicationDocumentsDirectory: NSURL = {
- let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory,inDomains: .UserDomainMask)
- return urls[urls.count - 1]
- }()
- /// Managed Object Model
- private lazy var managedObjectModel: NSManagedObjectModel = {
- let modelURL = NSBundle.mainBundle().URLForResource(self.modelName,withExtension: "momd")
- return NSManagedObjectModel(contentsOfURL: modelURL!)!
- }()
- /// Presistent Store Coordinator
- private lazy var psc: NSPersistentStoreCoordinator = {
- let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
- let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent(self.modelName)
- do {
- let options = [NSMigratePersistentStoresAutomaticallyOption:true]
- try coordinator.addPersistentStoreWithType(NSsqliteStoreType,configuration: nil,URL: url,options: options)
- }catch {
- print("添加持久化存储区错误")
- }
- return coordinator
- }()
- /// Managed Object Context
- lazy var context: NSManagedObjectContext = {
- var managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
- managedObjectContext.persistentStoreCoordinator = self.psc
- return managedObjectContext
- }()
- /**
- Save Context Data
- */
- func saveContext() {
- if context.hasChanges {
- do {
- try context.save()
- } catch let error as NSError {
- print("错误 ❌ \(error.localizedDescription)")
- abort()
- }
- }
- }
- }
选择ViewController.swift
添加下边代码import CoreData
添加属性:var managedContext: NSManagedObjectContext!
然后打开AppDelegate.swift
lazy var coreDataStack = CoreDataStack()
在application(_:didFinishLaunchingWithOptions:)
添加下边代码
- func application(application: UIApplication,didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
- let navigationController = window?.rootViewController as! UINavigationController
- let viewcontroller = navigationController.topViewController as! ViewController
- viewcontroller.managedContext = coreDataStack.context
- return true
- }
最后我们在 UIApplicationDelegate
的两个方法中调用存储方法
- func applicationWillTerminate(application: UIApplication) {
- coreDataStack.saveContext()
- }
- func applicationDidEnterBackground(application: UIApplication) {
- coreDataStack.saveContext()
- }
Modeling your data
打开Dog Walk
添加 Dog
Entity,添加属性 name
类型为 String
添加 Walk
Entity,添加属性 date
类型为 Date
接下来我们完成关系。
打开 Dog
Entity,添加relationship
name 为 walks
Set the destination to Walk
在属性版中修改Type
类型,To Many
,勾选 Ordered
打开 Walk
Entity,添加relationship
name 为 dog
relationship 为 Dog
Set the destination as dog and the inverse as walks.
Adding managed object subclasses
command + n
选择 NSManagedObject Subclass
选择 Dog Walk model
并且选中 Dog 和 Walk entities。 语言选择 Swift
我在生成的Walk.swift
和 Dog.swift
中都重写了父类的方法,为了在生成这两个类的时候有代码提示。
- override init(entity: NSEntityDescription,insertIntoManagedObjectContext context: NSManagedObjectContext?) {
- super.init(entity: entity,insertIntoManagedObjectContext: context)
- }
A walk down persistence lane
如果你上边的步骤都已经完成了,那么我们就可以开始存储数据了。
首先在ViewController.swift
中添加一个属性 var currentDog: Dog!
然后我们在viewDidLoad()
中来添加一些数据
- //创建一个 Entity
- let dogEntity = NSEntityDescription.entityForName("Dog",inManagedObjectContext: managedContext)
- let dogName = "Fido"
- //首先来检查在数据库中是否存在一个名为 Fido 的狗过
- let dogFetch = NSFetchRequest(entityName: "Dog")
- dogFetch.predicate = NSPredicate(format: "name == %@",dogName)
- do{
- //执行查询
- let results = try managedContext.executeFetchRequest(dogFetch) as! [Dog]
- //如果这个狗狗存在的话直接获取赋值给 currentDog
- if results.count > 0 {
- currentDog = results.first
- }else {
- //如果不存在 则实例化一个Dog
- currentDog = Dog(entity: dogEntity!,insertIntoManagedObjectContext: managedContext)
- currentDog.name = dogName
- try managedContext.save()
- }
- }catch let error as NSError{
- print("Error:\(error)" + "description:\(error.localizedDescription)")
- }
- @IBAction func add(sender: AnyObject) {
- //添加一个新的 Walk Entity into Core Data
- let walkEntity = NSEntityDescription.entityForName("Walk",inManagedObjectContext: managedContext)
- let walk = Walk(entity: walkEntity!,insertIntoManagedObjectContext: managedContext)
- walk.date = NSDate.timeIntervalSinceReferenceDate()
- //insert the new walk into the dog's walks set
- let walks = currentDog.walks!.mutableCopy() as! NSMutableOrderedSet
- walks.addObject(walk)
- currentDog.walks = walks.copy() as? NSOrderedSet
- //save the managed object context
- do {
- try managedContext.save()
- }catch let error as NSError {
- print("Could not save:\(error)")
- }
- tableView.reloadData()
- }
现在你运行程序,点击➕就可以看到有新的数据在列表中显示。
Deleting objects from Core Data
- func tableView(tableView: UITableView,commitEditingStyle editingStyle: UITableViewCellEditingStyle,forRowAtIndexPath indexPath: NSIndexPath) {
- if editingStyle == .Delete {
- //选择要删除的walk
- let walkToRemove = currentDog.walks![indexPath.row] as! Walk
- //删除
- managedContext.deleteObject(walkToRemove)
- do {
- //保存操作
- try managedContext.save()
- }catch let error as NSError {
- print("Could not save: \(error)")
- }
- // 删除视图中的数据
- tableView.deleteRowsAtIndexPaths([indexPath],withRowAnimation: .Automatic)
- }
- }
运行你的app 来试试吧。