SwiftでCoreData実装

プロジェクト作成時にUse Coredataにチェック入れてない状態から

##Data Modelファイル作成

###ファイル作成
`New file > Core Data > Data Model > RFCoreDataDemo.xcdatamodeld `

###Entity(テーブル)作成
`RFCoreDataDemo.xcdatamodeld > Add Entity`
EntityというEntity(テーブル)ができるので、好きな名前に編集。
(今回はPersonにした)

###CoreData特有の名前について
####Entity  
CoreDataのクラス定義でtableと同義。
リレーショナルDBでいうEmployees,Company

####Attributes  
Entityの情報。tableのフィールドと同義。
リレーショナルDBでいうEmployeesの name, position, salaryなど

####Relationship
複数のEntityをつなぐリンクの役割。
CoreDataでは1対1のEntityどうしをto-one relationships,
1対多数をto-many relationshipsと呼ぶ
managerはto-many relationshipsをemployeesに持ち、
個々のemployeeは to-one relationshipをmanagerに持つイメージ

###Attributes追加
Person EntitiyにAttribute追加
`+ > name > String(Type)`

##AppDelegateに追加
Use Coredataにチェック入れてると自動で生成されるコードを手動で追加

```Swift:AppDelegate.swift
// MARK: - Core Data stack

    lazy var applicationDocumentsDirectory: NSURL = {
        // The directory the application uses to store the Core Data store file. This code uses a directory named "jp.wandering.RFCoreDataDemo" in the application's documents Application Support directory.
        let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
        return urls[urls.count-1] as NSURL
    }()

    lazy var managedObjectModel: NSManagedObjectModel = {
        // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
        let modelURL = NSBundle.mainBundle().URLForResource("RFCoreDataDemo", withExtension: "momd")!
        return NSManagedObjectModel(contentsOfURL: modelURL)!
    }()

    lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
        // The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
        // Create the coordinator and store
        var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
        let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("RFCoreDataDemo.sqlite")
        var error: NSError? = nil
        var failureReason = "There was an error creating or loading the application's saved data."
        if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil, error: &error) == nil {
            coordinator = nil
            // Report any error we got.
            let dict = NSMutableDictionary()
            dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
            dict[NSLocalizedFailureReasonErrorKey] = failureReason
            dict[NSUnderlyingErrorKey] = error
            error = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
            // Replace this 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.
            NSLog("Unresolved error \(error), \(error!.userInfo)")
            abort()
        }
        
        return coordinator
    }()

    lazy var managedObjectContext: NSManagedObjectContext? = {
        // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
        let coordinator = self.persistentStoreCoordinator
        if coordinator == nil {
            return nil
        }
        var managedObjectContext = NSManagedObjectContext()
        managedObjectContext.persistentStoreCoordinator = coordinator
        return managedObjectContext
    }()

    // MARK: - Core Data Saving support

    func saveContext () {
        if let moc = self.managedObjectContext {
            var error: NSError? = nil
            if moc.hasChanges && !moc.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.
                NSLog("Unresolved error \(error), \(error!.userInfo)")
                abort()
            }
        }
    }

```

##データ読み書き
####使うViewでインポート
`import CoreData`

####データ保存
```Swift:ViewController.swift
func saveName(name: String){
        
        /* Get ManagedObjectContext from AppDelegate */
        let appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
        let managedContext: NSManagedObjectContext = appDelegate.managedObjectContext!
        
        /* Create new ManagedObject */
        let entity = NSEntityDescription.entityForName("Person", inManagedObjectContext: managedContext)
        let personObject = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedContext)
        
        /* Set the name attribute using key-value coding */
        personObject.setValue(name, forKey: "name")
        
        /* Error handling */
        var error: NSError?
        if !managedContext.save(&error) {
            println("Could not save \(error), \(error?.userInfo)")
        }
        println("object saved")
    }

```

####データロード
```Swift:ViewController.swift
func fetchPersonData() {
        
        /* Get ManagedObjectContext from AppDelegate */
        let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
        let manageContext = appDelegate.managedObjectContext!
        
        /* Set search conditions */
        let fetchRequest = NSFetchRequest(entityName: "Person")
        var error: NSError?
        
        /* Get result array from ManagedObjectContext */
        let fetchResults = manageContext.executeFetchRequest(fetchRequest, error: &error)
        if let results: Array = fetchResults {
            for obj:AnyObject in results {
                let name:String? = obj.valueForKey("name") as? String
                println(name)
            }
            println(results.count)
        } else {
            println("Could not fetch \(error) , \(error!.userInfo)")
        }
        
    }
```

####レコード更新
```Swift:ViewController.swift
func updateName(managedObject: NSManagedObject, newName: String) {
        
        /* Get ManagedObjectContext from AppDelegate */
        let appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
        let managedContext: NSManagedObjectContext = appDelegate.managedObjectContext!
        
        /* Change value of managedObject */
        managedObject.setValue(newName, forKey: "name")
        
        /* Save value to managedObjectContext */
        var error: NSError?
        if !managedContext.save(&error) {
            println("Could not update \(error), \(error!.userInfo)")
        }
        
        println("Object updated")
    }


```

####レコード削除
```Swift:ViewController.swift
func deleteName(managedObject: NSManagedObject) {
        
        /* Get ManagedObjectContext from AppDelegate */
        let appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
        let managedContext: NSManagedObjectContext = appDelegate.managedObjectContext!
        
        /* Delete managedObject from managed context */
        managedContext.deleteObject(managedObject)
        
        /* Save value to managed context */
        var error: NSError?
        if !managedContext.save(&error) {
            println("Could not update \(error), \(error!.userInfo)")
        }
        println("Object deleted")
        
    }

```

それぞれの処理はこんな感じ
Viewに各ボタンを配置し、それぞれにこのメソッドを実行させると、Logに出てきます。

全コードはこちら
https://github.com/ryusukefuda/CoreData-Swift-Demo